Glossary
From A for acetylcholine to Z for zonular fibers, the glossary contains important terms relating to the brain. It provides a brief explanation and the option to view all content related to the selected term – from texts and glossary entries to research groups, videos, and animations from the media library.
Acetylcholine
Acetylcholine is one of the most important neurotransmitters in the nervous system. In the central nervous system, it is involved in attention, learning, and memory; in the peripheral nervous system, it transmits excitation from nerves to muscles at the neuromuscular end plates and controls processes of the autonomic nervous system, i.e., the sympathetic and parasympathetic parts. Areas in which acetylcholine acts as a messenger substance are called cholinergic. It was the first neurotransmitter to be discovered, identified in 1921 by Otto Loewi in the heart of a frog.
Acetylsalicylic acid
Pharmaceutical active ingredient for pain, fever, and inflammation – the best-known pain reliever containing this active ingredient is aspirin.
Adaptation
Adaptation refers to the process by which the sensory organs, the perceptual system, or the entire organism adjusts to the intensity and quality of stimuli and to changes in environmental conditions. In visual adaptation, for example, the pupil and the sensitivity of the photoreceptors regulate themselves according to the prevailing light conditions.
Anterior pituitary
The adenohypophysis is a gland and is also referred to as the "anterior pituitary gland." The adenohypophysis produces hormones such as prolactin and releases them directly into the blood, meaning it is endocrine. It is therefore involved in regulating numerous physiological processes. Together with the neurohypophysis, which is part of the brain, it forms the pituitary gland. The two systems are closely linked via a contact surface.
Adrenaline
Along with dopamine and norepinephrine, it belongs to the catecholamines. Adrenaline, also known as epinephrine, is the classic stress hormone. It is produced in the adrenal medulla and causes an increase in heart rate and heartbeat strength, thus preparing the body for increased stress. In the brain, adrenaline also acts as a neurotransmitter (messenger substance), where it binds to so-called adrenoreceptors.
Afferent nerve fiber
Afferent refers to nerve fibers that carry information to the central nervous system. Afferent nerve fibers transmit sensory information from the periphery, such as pain, temperature, touch, muscle tension, or organ activity, to the central nervous system. The opposite is efferent.
Agnosia
The term agnosia comes from Latin and means "not knowing." It is a disorder of recognition caused by damage or dysfunction of the brain, without deficits in sensory perception. Agnosia is usually very specific, such as prosopagnosia, the inability to recognize a person by their face.
Accommodation
Change in the thickness of the lens of the eye by the ciliary muscles. This adjustment process increases the refractive power of the lens, allowing objects at different distances to be seen clearly.
Action potential
In excitable cells (e.g., neurons or muscle cells), very rapid changes in electrical potential occur across the cell membrane. This event is the basis for signal conduction along the axon of the nerve cell. The action potential continues along the cell membrane and, according to the all-or-nothing principle, only occurs when the cell has been sufficiently excited.
All-or-nothing principle
According to this principle, an electrical potential is only triggered in the cell when a certain threshold value of stimulus intensity has been exceeded. The response either occurs completely or not at all.
Allocortex
A phylogenetically ancient region of the cortex (cerebral cortex) which, unlike the isocortex (also called neocortex), has fewer than six cell layers – in the hippocampus, for example, only three. The allocortex is divided into the paleocortex and archicortex, as well as the periallocortex, which is a transitional form between the allocortex and isocortex.
Alpha waves
Neuroscientists distinguish between different types of brain waves based on their frequency. Alpha waves oscillate in the mid-frequency range between approximately 8 and 12 hertz. They occur, for example, in a relaxed waking state, such as when test subjects are tired or have their eyes closed, i.e., when there is no mental activity. In the brain, they originate primarily in the parietal lobe. They are also called "Berger's waves" Hans Berger, who first described them.
Amacrine cells
Amacrine cells are interneurons of the retina. They are located between photoreceptors and bipolar cells on the one hand and ganglion cells on the other. The name was coined by Ramón y Cajal and means "without axon."
Anvil
The middle of the three ossicles in the middle ear transmits the vibration from the malleus to the stapes.
amnesia
A form of memory disorder that affects the memory for facts and events. The unconscious memory for, for example, sensorimotor skills such as driving a car or riding a bike remains intact.
Ampakine
A group of active substances that belong to the "neuroenhancers" and can improve cognitive performance. Among other things, they increase attention span, promote memory, and facilitate learning processes. Their effect is based on binding to AMPA receptors in the brain, which facilitates synaptic transmission at glutamatergic synapses and enhances overall neuronal signal transmission.
Amygdala
An important core area in the temporal lobe that is associated with emotions: it evaluates the emotional content of a situation and reacts particularly to threats. In this context, it is also activated by pain stimuli and plays an important role in the emotional evaluation of sensory stimuli. Inaddition, it is involved in linking emotions with memories, emotional learning ability, and social behavior. The amygdala is part of the limbic system.
Anosognosia
Literally, the term from Greek means "not recognizing" one's own neurological disease – for example, hemiplegia or deafness. Instead, patients confabulate (invent) reasons for the disorder or deny the disease altogether. Anosognosia usually occurs after damage to the right hemisphere in the fronto-parietal and insular areas and usually resolves after a few months.
Antagonist
Due to the lock-and-key principle, transmitters (messenger substances) can only bind to specific receptors. An antagonist can be so similar to this transmitter that it can bind to this receptor. It thus prevents the actual transmitter from activating the receptor and becoming effective. There are also antagonists that do not bind directly to the receptor but alter the "lock," i.e., the receptor, so that the key no longer fits.
Anterior cingulate cortex
The anterior cingulate cortex (cingulate gyrus) plays a role not only in autonomic functions such as blood pressure and heart rate regulation, but also in rational processes such as decision-making. This area of the brain is also involved in emotional processes, such as impulse control. Anatomically, the anterior cingulate cortex (ACC) is characterized by a large number of spindle neurons (Von Economo neurons). These special nerve cells have a long, spindle-shaped structure and have so far only been found in mammals such as primates, elephants, and some whale and dolphin species. Spindle neurons contribute to higher social and emotional processes such as self-awareness, empathy, and quick emotional decisions. In pain perception, it is particularly associated with the affective component of pain – including social pain, such as that experienced through exclusion.
Anterograde amnesia
A form of memory disorder in which the formation of new memories – i.e., the storage of new information – is no longer possible from the time of the damage. Memories from before that time can still be recalled. Those affected usually also forget their forgetfulness.
Apraxia
Difficulty performing a purposeful movement, such as grasping a glass or cutting with scissors. Depending on the form of apraxia, speech or facial expressions may also be affected. The cause is not muscle weakness or paralysis, but damage to one or more areas of the brain, e.g., as a result of a stroke. In other cases, however, it is congenital.
Archicortex
An ancient structure of the cerebrum in terms of evolutionary development, which, in contrast to the isocortex (also called the neocortex), has a three-layer structure. The archicortex mainly comprises the hippocampal structures.
Area F5
A part of the ventral premotor cortex located in the frontal lobe of the mammalian brain. The nerve cells in this region of the brain are involved in planning and organizing purposeful movements, especially of the mouth and hand/grasping movements. Area F5 also has historical significance: it was here that researchers first discovered mirror neurons in macaques – the nerve cells in the brains of primates that fire just as strongly when their owners observe an action as when they perform it themselves.
Asomatognosia
Asomatognosia literally means "not knowing" one's own body. The term refers to the loss of perception or feeling of belonging to one's own body parts. Asomatognosia is usually caused by damage to the right parietal lobe, which means that the left side of the body is usually affected.
Association cortex
Parts of the cerebrum that are not assigned to the primary and secondary areas for sensory processing and motor function. They are mainly located in the neocortex, integrate information from multiple sources, are the center of thalamocortical and cortico-cortical networks, and cannot be clearly distinguished functionally.
Astrocyte
Astrocytes are among the largest glial cells. Their tasks include maintaining the blood-brain barrier and reabsorbing released neurotransmitters (messenger substances in the brain).
Ataxia
A medical umbrella term for the disturbance or loss of coordination of movement. In the case of target ataxia, for example, a targeted grasp of an object may be slow, shaky, or too fast. Ataxia can be congenital or the result of lesions or degeneration.
Auditory cortex
The auditory cortex is a part of the temporal lobe that is involved in processing acoustic signals. It is divided into the primary and secondary auditory cortex.
attention
Attention serves as a tool for consciously perceiving internal and external stimuli. We achieve this by focusing our mental resources on a limited number of stimuli or pieces of information. While some stimuli automatically attract our attention, we can select others in a controlled manner. The brain also unconsciously processes stimuli that are not currently the focus of our attention.
Autism
A serious developmental disorder that often manifests itself in reduced social skills, impaired communication, and stereotypical behavior. Today, it is understood to be part of the autism spectrum disorders.
Autonomic nervous system
The part of the nervous system that primarily controls unconscious vital functions such as breathing, heartbeat, and blood pressure. The autonomic nervous system is divided into the sympathetic nervous system, which is active in performance and stress situations, and the parasympathetic nervous system, which is active during rest and recovery phases. In some cases, the enteric nervous system, which is responsible for gastrointestinal functions, is also considered part of the autonomic nervous system.
Axon
The axon is the extension of the nerve cell that is responsible for conducting nerve impulses to the next cell. An axon can branch out many times, reaching a large number of downstream nerve cells. It can be more than a meter long. The axon ends in one or more synapses.
Ammon's horn
Part of the cerebrum, specifically the front end of the hippocampus. The Cornu Ammonis is divided into fields CA1 to CA4. It owes its name to its shape, which resembles the horn of an ammon sheep.
Angular gyrus
The angular gyrus is part of the cerebrum and is considered part of the parietal lobe. Anatomically, however, it is located at the intersection of the temporal, occipital, and parietal lobes. Functionally, visual and auditory impressions are integrated here, and it is also involved in writing, reading, and arithmetic.
Auditory pathway
The auditory pathway refers to the nerve fibers that transmit acoustic information from the inner ear to the primary auditory cortex. In humans, the auditory pathway consists of five switching points: the spiral ganglion, the auditory nuclei in the brainstem, the inferior colliculus, the medial geniculate body of the thalamus, and the primary auditory cortex.
Auditory nerve
The hair cells of the organ of Corti stimulate neurons in the spiral ganglion, which is located in the cavity of the cochlea. Their axons form the auditory nerve, which transmits electrical impulses from the inner ear to the brain. Together with the vestibular nerve (nervus vestibularis), the auditory nerve forms the VIII cranial nerve.
Acoustic radiation
The acoustic radiation is part of the auditory pathway, i.e., the areas of the brain involved in hearing. More specifically, it is the section located between the thalamus and the sensory cortex.
Alzheimer's disease
Alzheimer's disease is a progressive neurodegenerative disorder characterized by cortical atrophy, nerve cell loss, synapse loss, and deposits of amyloid plaques and neurofibrillary tangles, leading to dementia and loss of function. Early symptoms include memory problems, speech disorders, executive deficits, depressive moods, and subtle personality changes. As the disease progresses, global cognitive impairment, aphasia, agnosia, apraxia, and behavioral abnormalities such as apathy, restlessness, and sleep disorders occur. The disease was first described in 1907 by Alois Alzheimer.
Afterimage
An image that is perceived after the actual image is no longer present. An afterimage normally occurs when you have stared at an image for about a minute. In the case of positive afterimages, the image has similar brightness and colors to the original. Negative afterimages occur more frequently: when looking at a white surface, the image previously viewed appears there in the respective complementary color. Afterimages are caused by the "overfatigue" of the photoreceptors, which stop sending signals to the brain after a certain period of viewing.
Anterior nuclei
This anterior, or front, core group of the thalamus maintains fiber connections with limbic areas, especially the hippocampus and the cingulate gyrus. It is considered an important hub of the limbic system.
Anterior cingulate cortex
Like the entire cingulate cortex, the anterior region of the limbic system regulates drive-controlled behavior. In the perception of pain, it is particularly associated with the affective pain component - including social pain as experienced through exclusion.
Basal ganglia
The basal ganglia are a group of subcortical nuclei (located beneath the cerebral cortex) in the telencephalon. The basal ganglia include the globus pallidus and the striatum, and, depending on the author, other structures such as the substantia nigra and the subthalamic nucleus. The basal ganglia are primarily associated with voluntary motor function, but they also influence motivation, learning, and emotion.
Basilar membrane
The basilar membrane runs through the cochlea for a length of approximately 34 mm. It is stretched like the string of a violin, narrow and stiff at the base and wider and more flexible at the apex. Incoming sound frequencies cause it to vibrate. This movement is picked up by the hair cells in the organ of Corti and converted into nerve impulses.
Basic emotions
Some theories assume that all emotions can be broken down into a few basic emotions. These are also referred to as primary emotions. According to Ekman, these classically include fear, anger, joy, sadness, disgust, and surprise. Primary emotions arise very quickly in response to an event and sometimes subside just as quickly. Over time, they can transition into secondary emotions (e.g., shame, guilt, or pride).
Beta-amyloid
A peptide consisting of 36 to 42 amino acids that is considered the main component of senile plaques and is believed to be responsible for the development of Alzheimer's disease. The starting product is the amyloid precursor protein (APP). Certain enzymes in the cell membrane cut the precursor protein into peptides of various sizes. Amyloids consisting of 40 and 42 amino acids are found in senile plaques, with the 42-amino-acid product forming aggregates particularly quickly, at least in the Petri dish. The normal function of beta-amyloid has not yet been conclusively clarified.
Beta waves
Electrical activity of the brain (brain waves) measured on the surface of the head or using electrodes implanted in the brain itself. If the frequency range of the measured activity is between 13 and 30 Hz, these are called beta waves. They are associated with normal waking states and alertness.
Betz giant cells
Betz giant cells are particularly large pyramidal cells in the primary motor cortex (area 4). They have very large cell bodies with a diameter of 100 µm and heavily myelinated axons that project directly into the spinal cord. This makes them part of the corticospinal neurons of the pyramidal tract. Although they make up only a small portion of the fibers of the pyramidal tract, they are functionally important for the control of voluntary movements, especially fine motor skills.
Biomarker
In medicine, a biomarker is a substance that provides information about the physiological state of an organism. Biomarkers can either be produced in the body itself or describe chemical compounds that doctors introduce into the body to test certain physiological functions. Several indicators, for example, are being discussed as possible biomarkers for Alzheimer's disease. These include the concentration of soluble amyloid precursor protein in the blood and the activity of the enzyme that cleaves the precursor protein to produce plaque-forming beta-amyloid. Disease-related changes detected by imaging techniques are also often referred to as biomarkers. For example, the breakdown of brain tissue can be detected by MRI.
Bipolar cells
The bipolar cell is a bipolar neuron, i.e., a neuron with one axon and one dendrite located in the middle layer of the retina. It transmits sensory information from the photoreceptors to the ganglion cells.
Bitter receptors
One of several groups of sensors that specialize in perceiving a specific taste quality. The sensory cells in which the taste receptors perform their function are located in the taste buds on the tongue and in the surrounding mucous membranes. Bitter receptors belong to the family of G protein-coupled receptors. A single cell can contain several different bitter receptors. As a result, it responds to different bitter substances with the same signal. This makes it very difficult for us to distinguish between individual bitter substances in terms of taste.
Blind spot
A blind spot in visual perception caused by the anatomy of the eye: since the optic nerve leaves the eye at the optic disc, there are no photoreceptors there – and no perception can occur. This blind spot is not consciously perceived.
Blood-brain barrier
A selectively permeable membrane formed by cells in the walls of the capillary blood vessels in the brain. It protects the brain from harmful substances in the blood, but allows nutrients and oxygen to pass from the blood into the brain.
Brain-computer interface
A direct interface between the brain and a computer. There are various approaches to developing brain-computer interfaces: invasive – via an electrode in the brain – as well as non-invasive – via EEG. They enable locked-in patients, for example, to communicate again. Another area of application is the control of arm or leg prostheses via peripheral nerves.
Broca's area
An area of the prefrontal cortex (cerebral cortex) that is usually located in the left hemisphere. Plays a key role in the motor production of speech. First described by French neurologist Paul Pierre Broca in 1861.
Brodmann area
As early as 1909, neuroanatomist Korbinian Brodmann divided the cerebral cortex into different areas. He did this based on histological criteria, distinguishing these areas according to their cellular structure. It later became apparent that these different structures of the cortex are often associated with different specializations.
Brightness
Brightness is one of the dimensions of visual perception: the perception of light intensity. It influences the size of the pupil.
Brain stem
The "trunk" of the brain, to which all other brain structures are "attached," so to speak. From bottom to top, it comprises the medulla oblongata, the pons, and the mesencephalon. It transitions into the spinal cord below. It is a center for vital functions such as breathing and heartbeat and contains ascending and descending pathways between the cerebrum, cerebellum, and spinal cord.
Basket cell
Basket cells are interneurons in the cerebellum and hippocampus. In the cerebellum, they are excited by parallel fibers and in turn inhibit Purkinje cells.
Body schema
The body schema is the dynamic representation of one's own body, which is based on proprioceptive, visual, and tactile information, but goes beyond it. Disorders such as phantom limb sensations after amputations show that the body schema can exist independently of current sensory inputs.
Basal nucleus
A collection of nerve cells in the basal region of the telencephalon. The basal ganglia are considered to be an important producer of the neurotransmitter acetylcholine. In Alzheimer's patients and, in some cases, Parkinson's patients, the basal ganglia degenerate. As a result, they produce less and less acetylcholine, which neurologists associate with some of the symptoms of these diseases.
Basal nucleus, lateral part
The pars lateralis refers to the lateral part of the basal nucleus, i.e., the part located on the side.
Basal nucleus, medial part
Medial part = medial part of Meynert's basal nucleus.
Bulbous corpuscle
Bulbous corpuscles – or Ruffini corpuscles – are slow mechanoreceptors that detect skin stretching and joint movements.
Caenorhabditis elegans
The nematode Caenorhabditis elegans is a well-known and popular model organism in genetics. This is not least because each adult animal has exactly 1031 cell nuclei and its nervous system consists of exactly 302 nerve cells. It is only about a millimeter long and lives in the soil in temperate zones.
cAMP
Cyclic adenosine monophosphate is produced from ATP by the enzyme adenylyl cyclase. It is a second messenger in intracellular signal transduction. In particular, it serves to activate protein kinase A. These trigger the activation of enzymes and genes.
Cannon-Bard theory
An emotion theory developed by Walter Cannon and Philip Bard in 1927/1928 which, in contrast to the James-Lange theory of 1884/85, assumes that emotions are independent of emotional expression and arise through the thalamus. This means that when there is a loud bang, the subjective feeling of fear occurs in parallel with trembling or a racing heart, not as a result of each other. It is also known as the "thalamic theory of emotion."
Capgras syndrome
Perceptual disorder in which loved ones – e.g., parents or children – are perceived as "not real." Patients often assume that they have been replaced by doppelgangers or robots.
Cerebellum
The cerebellum is an important part of the brain, located at the back of the brain stem and below the occipital lobe. It consists of two cerebellar hemispheres covered by the cerebellar cortex and plays an important role in motor processes, among other things. It develops from the rhombencephalon.
Cerebrospinal fluid
A clear fluid that fills the ventricular system and bathes the brain and spinal cord in the subarachnoid space, protecting them from impact. Three to five times a day, 100 to 160 ml of fluid is renewed by the choroid plexus. Certain diseases are reflected in the composition of the cerebrospinal fluid.
CGRP
The abbreviation stands for calcitonin gene-related peptide. It refers to a messenger substance in the nervous system that consists of 37 amino acids. CGRP is produced in both the central and peripheral nervous systems. The peptide dilates the blood vessels. Migraine patients often have elevated CGRP levels. The effect of CGRP is of interest for other diseases, such as circulatory disorders or coronary heart disease.
Change blindness
Change blindness is a phenomenon of visual perception whereby changes in the environment are not noticed. It is a problem of attention that can also arise due to distraction or concentration on other things. In experiments, a scene that changes during masking or distraction is often shown. Test subjects are unable to perceive the change.
Chemoreceptor
Receptor that responds to chemical stimuli, e.g., taste or smell receptors. Chemoreceptors are also found in internal organs, such as the intestines and liver.
cholinergic
Cholinergic neurons produce acetylcholine (an important neurotransmitter in the brain), and cholinergic synapses use it to transmit signals.
Cingulate cortex
A component of the prefrontal cortex located at the front of the brain. Like half a doughnut, the cingulate cortex wraps around the corpus callosum. Functionally, it belongs to the limbic system and is involved in emotion, memory, and motor function.
Cochlea
The cochlea is the part of the inner ear that contains the organ of Corti, which is responsible for converting acoustic signals into nerve impulses.
Cochlear nuclei
These nuclei on the dorsolateral side of the brainstem are innervated by the auditory nerve and form a switching center for information from the auditory system. The efferent neurons of the cochlear nuclei transmit auditory information to downstream switching centers in the brainstem, such as the inferior colliculi.
Corpus callosum
As the largest commissure (connection in the brain), the corpus callosum connects the two cerebral hemispheres. It consists of 200-250 million nerve fibers and serves to exchange information.
Cortex
Cortex refers to a collection of neurons, typically in the form of a thin surface. However, it usually refers to the cerebral cortex, the outermost layer of the cerebrum. It is 2.5 mm to 5 mm thick and rich in nerve cells. The cerebral cortex is heavily folded, comparable to a handkerchief in a cup. This creates numerous convolutions (gyri), fissures (fissurae), and sulci. Unfolded, the surface area of the cortex is approximately 1,800cm².
Corti’s organ
The organ of Corti is part of the cochlea (hearing organ) in the inner ear. Here, sound waves are picked up by hair cells and converted into nerve impulses.
Cortical cell layers
The cortical cell layers form the structure of the cerebral cortex and cerebellar cortex. In the cerebral cortex, the number of layers varies, reaching a maximum of six in the neocortex. These six layers differ in terms of cell types and interconnections.
Cortisol
A hormone produced by the adrenal cortex that is primarily an important stress hormone. It belongs to the group of glucocorticoids and influences carbohydrate and protein metabolism in the body, suppresses the immune system, and acts directly on certain neurons in the central nervous system.
CREB
A transcription factor in the cell nucleus that is activated by cAMP-dependent signaling pathways. CREB influences gene activity and can thus improve communication between two cells. This is a cellular basis for learning processes.
Color blindness
The inability to perceive colors. Instead, those affected only see brightness. This can be caused by hereditary cone blindness or a retinal disease, for example, but also by damage to the optic nerves or visual association areas.
Color consistency
A correction mechanism that ensures the relatively constant appearance of an object's color under different lighting conditions. This means that the red of a rose appears the same in the morning as it does in the evening, even though the light changes depending on the time of day and weather conditions.
Color tone
One of the dimensions of color perception: the dominant wavelength.
Cerebrum
The cerebrum comprises the cerebral cortex (gray matter), the nerve fibers (white matter), and the basal ganglia. It is the largest part of the brain. The cortex can be divided into four cortical areas: the temporal lobe, frontal lobe, occipital lobe, and parietal lobe.
Its functions include the coordination of perception, motivation, learning, and thinking.
Cingulate gyrus
The cingulate gyrus is an important part of the limbic system in the cerebrum. This strip of cortex runs medially in the cerebrum, directly above the corpus callosum. Among other things, it is involved in emotions and memory. Through its connections to limbic and autonomic centers, it can also influence autonomic responses (e.g., heart rate, blood pressure). The anterior (front) region in particular is also associated with attention, motivation, error monitoring, and emotion regulation.
Cranial nerve
A group of 12 pairs of nerves that originate directly in the brain, mostly in the brain stem. They are numbered with Roman numerals (I–XII). Unlike the rest, the first and second cranial nerves (olfactory and optic nerves) are not part of the peripheral nervous system, but rather the central nervous system.
Cornea
The cornea is the transparent front part of the outer layer of the eye. It is involved in refracting light, ensuring that the image of a distant object falls on the point of sharpest vision on the retina.
caudal
A positional term – caudal means "towards the tail." In relation to the nervous system, it refers to a direction along the neural axis, i.e., towards the rear.
In animals (that do not walk upright), the term always means: located at the end of the spine. Due to the upright gait of humans, the brain bends in relation to the spinal cord, which means that caudal also means downward.
Classical conditioning
According to Zimbardo's definition (1999), classical conditioning is a form of learning in which one stimulus or event predicts the occurrence of another stimulus or event. The organism learns a new association between two stimuli – between a stimulus that did not previously trigger the response and another stimulus that triggers the response according to the laws of nature. The best-known example is Pavlov's dog, which salivated when a bell rang.
Cerebellar hemispheres
Like the cerebrum, the cerebellum also has two hemispheres. The hemispheres are primarily responsible for finely tuned, purposeful movement control.
Cerebellar nuclei
A group of four paired nuclei located in the white matter of the cerebellum: the dentate nucleus, emboliform nucleus, globose nucleus, and fastigial nucleus. Functionally, the cerebellar nuclei are associated with motor tasks.
Cerebellar peduncles
Three fiber connections on the right and left sides that connect the cerebellum to the brain stem. All afferent and efferent fibers of the cerebellum run through these connections.
Climbing fiber
Climbing fibers are the axons (long fiber-like extensions of nerve cells) of neurons in the inferior olive nucleus of the brain stem. They extend into the cerebellum and "climb" along the Purkinje cells, with which they form synaptic connections.
Collaterals
Collaterals are the side branches or secondary branches of blood vessels and axons.
Commissure
A commissure is a fiber connection between two anatomical areas, primarily from one hemisphere to the other. The largest commissure in the human brain is the corpus callosum.
Corpus callosotomy
A surgical procedure in which the corpus callosum, the bridge between the two hemispheres of the brain, is severed. This interrupts the flow of information between the two hemispheres. Commissurectomy was previously performed mainly for the purpose of controlling epileptic seizures.
Complementary colors
A term from color theory: Complementary colors are pairs of colors that, when mixed, produce white or neutral gray. They are always opposite each other on the color wheel. Different pairings are named depending on the color model.
Complex cell
A nerve cell in the primary visual cortex with large receptive fields. They respond to visual stimuli with appropriate contrast, a specific orientation, and often also a specific direction of movement.
Confabulation
Confabulation refers to a memory or explanation that the person concerned is completely convinced is true, but which is objectively false. There is no conscious intent to deceive behind this. The cause is usually medical, such as damage to the orbitofrontal or other frontal brain areas, amnestic syndrome (e.g., Korsakoff's syndrome), traumatic brain injury, or dementia.
Consolidation
Consolidation refers to the process by which new information, memories, or learning content is stabilized and stored in the brain for the long term.
contralateral
Contralateral is a positional term. It means "located on the other side of the body."
Convergence
Convergence of neurons occurs when several neurons are connected synaptically to a single transmitting neuron. In the eye, for example, information received by up to 130 receptors is transmitted to only one neuron in the retina. The opposite is divergence, when one neuron transmits signals to several other neurons.
cranial
A positional term – cranial means "towards the head." In relation to the nervous system, it refers to a direction along the neural axis, i.e., forward.
In animals (without upright gait), the designation is simpler, as it always means forward. Due to the upright gait of humans, the brain bends in relation to the spinal cord, where cranial also means "upward."
Caudate nucleus
Part of the basal ganglia, it forms the striatum together with the putamen. Anatomically, the caudate nucleus is located frontally in the center of the brain and extends backward, forming a C shape. It consists of a head (caput nuclei caudati), a body (corpus nuclei caudati), and a tail (cauda nuclei caudati). In contrast to the more motor-related parts of the basal ganglia, this area is strongly connected to the prefrontal cortex in addition to its motor functions. As a result, this part of the striatum is also heavily involved in cognition, motivation, and emotion.
Central nucleus
The nucleus centralis belongs to the centromedial nucleus group of the amygdala. It has connections to the hypothalamus and nuclei of the brain stem and is involved in autonomous emotional responses such as fear reactions.
Cortical nucleus
The cortical nucleus is one of the cortical nuclei of the amygdala. It primarily receives olfactory information and projects to the hypothalamus, entorhinal cortex, and insula, among other areas.
Cortical blindness
When the primary visual cortex is destroyed, those affected are effectively blind, even though their eyes are undamaged. However, they are often unconsciously able to grasp and catch objects and even name them when asked to guess. This effect is known as blind sight.
Criminal responsibility
In a neuroethical context, the issue of "culpability" arises from the question of whether humans possess free will: only when someone commits an act of their own free will can it be morally evaluated. Based on their research findings, some leading neuroscientists argue that humans do not possess free will. According to this view, even criminals are not responsible for their actions. If this way of thinking were to prevail, it would have significant legal implications in addition to moral ones.
Calcarine sulcus
Cerebral sulcus that divides the median, inwardly located portion of the occipital lobe.
Cones
The cones are a type of photoreceptor in the retina. The three different types of cones – S, M, and L – are each stimulated by short, medium, and long wavelengths of visible light, enabling color vision. They are highly concentrated in the fovea and enable sharp vision.
Cerebellar cortex
The cortex of the cerebellum, which, like that of the cerebrum, is composed of gray matter, or nerve cells. It consists of three layers and is highly folded, creating what are known as foliae, or leaves.
Ciliary muscle
Through its activity via the zonular fibers, the ciliary muscle changes the curvature of the lens, thereby enabling accommodation (adjustment).
declarative memory
Declarative memory is a form of long-term memory. Based on content, two types are distinguished: episodic memory – the stories of our lives – and semantic memory, or factual knowledge. What both have in common is that their respective contents can be put into words, i.e., described.
dementia
Dementia is an acquired deficit of cognitive, social, motor, and emotional abilities. The most well-known form is Alzheimer's disease. "De mentia" means "without mind" in English.
Dendrite
Tree-like branching area of nerve cells whose extensions act as a kind of antenna for receiving electrical impulses from other cells.
Dendritic spines
Mushroom- or button-shaped protrusions on dendrites, at the tip of which there is usually a synapse, which is the site of communication between two nerve cells. The spines increase the surface area of dendrites, which thus have space for additional synapses. They play an important role in synaptic plasticity. The dendritic spines can swell and shrink depending on activation.
Depolarization
The decrease in membrane potential (towards 0 mV) from the resting potential, which is measured between the inside of the cell and the outside space and has a difference of -70 mV.
Depression
A mental illness whose main symptoms are sadness and a loss of joy, motivation, and interest. Current classification systems distinguish between different types of depression.
Dermatome
Describes an area of skin that is connected to exactly one spinal nerve (a nerve originating in the spinal cord).
Diencephalon
The diencephalon (midbrain) includes the thalamus and hypothalamus, among other structures. Together with the cerebrum, it forms the forebrain. The diencephalon contains centers for sensory perception, emotion, and the control of vital functions such as hunger and thirst.
diffusion tensor imaging
Diffusion tensor imaging (DTI) is a form of magnetic resonance imaging. It enables researchers and physicians to visualize how water distributes itself in space over time, allowing them to reconstruct nerve pathways in the brain, for example. Certain changes, such as those caused by a stroke, can be detected more effectively with diffusion tensor imaging than with conventional magnetic resonance imaging.
Dopamine
Dopamine is an important neurotransmitter in the central nervous system that belongs to the catecholamine group. It plays a role in motor function, motivation, emotion, and cognitive processes. Disruptions in the function of this transmitter play a role in many brain disorders, such as schizophrenia, depression, Parkinson's disease, and substance dependence.
dorsal
The positional term dorsal means "towards the back." In relation to the nervous system, it refers to a direction perpendicular to the neural axis, i.e., upwards towards the head or backwards.
In animals that do not walk upright, the term is simpler, as it always means toward the back. Due to the upright posture of humans, the brain bends in relation to the spinal cord, making dorsal mean "upward."
Dorsolateral PFC
The dorsolateral prefrontal cortex is the upper (dorsal) and lateral part of the frontal lobe. It is involved in the planning and regulation of complex motor and intellectual actions. According to one experiment, this also seems to include lying. The dorsolateral PFC regulates these and other abilities in coordination with many other areas of the brain with which it is closely linked.
Duchenne smile
The kind of smile where not only the corners of the mouth turn upward, but the muscles around the eyes also create laugh lines. It is considered the only genuine, unfeigned smile. Named after the French physiologist of the same name.
Dura mater
The outermost of the three membranes covering the brain and spinal cord. Consists of connective tissue.
dysdiadochokinesia
Medical professionals understand dysdiadochokinesia to be the limitation of the ability to perform rapid successive movements. The disorder is usually accompanied by lesions in the cerebellum, caused, for example, by a stroke.
Dentate gyrus
The dentate gyrus is part of the hippocampus and acts as its "input station." It receives various sensory inputs from the cortex (cerebral cortex) via the entorhinal cortex. Its densely packed granule cells, which are found in the so-called granular layer, project almost exclusively to the CA3 region of the hippocampus.
Dorsal thalamus
The thalamus is the largest structure in the diencephalon and is located above the hypothalamus. The thalamus is considered the "gateway to consciousness" because its nuclei are the transit station for all information to the cortex (cerebral cortex) – except for olfactory information, which first reaches the olfactory areas of the brain directly. At the same time, they also receive massive cortical inputs so it might be better to regard this a thalami-cortical system. The nuclei of the thalamus are grouped together. The term "gateway to consciousness" also refers to attention control, sleep-wake regulation, and consciousness modulation by the intralaminar nuclei.
Dorsal pathway
The dorsal visual processing pathway is the part of visual information processing that is responsible for the spatial localization of objects and the perception of movement. It transmits visual information from the primary visual cortex (V1) and secondary visual areas (V2, V3) to the parietal lobes, where spatial orientation, motion analysis, and action planning take place.
Eye
The eye is the sensory organ responsible for perceiving light stimuli – electromagnetic radiation within a specific frequency range. The light visible to humans lies in the range between 380 and 780 nanometers.
Eyeball layers
The layers of the eye form the wall of the eyeball. They can be roughly divided into three areas: the outer membrane with the cornea and sclera, the middle membrane with the iris, choroid, and ciliary body, and the inner membrane with the photoreceptive and blind parts of the retina.
EEG
An electroencephalogram, or EEG for short, is a recording of the brain's electrical activity (brain waves). Brain waves are measured on the surface of the head or using electrodes implanted in the brain itself. The time resolution is in the millisecond range, but the spatial resolution is very poor. The discoverer of electrical brain waves and EEG is the neurologist Hans Berger (1873−1941) from Jena.
Efference
An axon (long, fiber-like extension of nerve cells) that conducts signals away from the central nervous system to peripheral areas, as is the case with motor function, for example, is called efferent. The opposite is afferent.
Eidetic memory
The term eidetic memory refers to the phenomenon of near-perfect visual memory. The term "photographic" memory is also sometimes used. The phenomenon is very rare, but has not been clearly defined scientifically.
Electroconvulsive therapy
A therapeutic procedure with temporary positive effects, used primarily for severe or treatment-resistant depression and catatonia. Electroconvulsive therapy (ECT) – colloquially referred to as "electroshock therapy" – was developed in the 1930s. Under controlled conditions, electrical stimulation triggers a brief epileptic seizure, which causes neurobiological changes. It is performed exclusively under general anesthesia and muscle relaxation.
Electrooculogram
The electrooculogram is a recording of the electrical potential of the eyes. It is measured by electrodes placed on the skin around the eye. A method for measuring retinal function and, indirectly, eye movement.
Embodied cognition
A term from cognitive science that describes how physical states affect the mind. Embodied cognition can be translated as "physically anchored cognition" or "embodied thinking." The mind, body, and environment are understood as parts of a dynamic system in which cognitive processes occur as complex interactions between the components. For example, gesturing can support mathematical abilities.
emotions
Neuroscientists understand "emotions" to be complex response patterns that include experiential, physiological, and behavioral components. They arise in response to personally relevant or significant events and generate a willingness to act, through which the individual attempts to deal with the situation. Emotions typically occur with subjective experience (feeling), but differ from pure feeling in that they involve conscious or implicit engagement with the environment. Emotions arise in the limbic system, among other places, which is a phylogenetically ancient part of the brain. Psychologist Paul Ekman has defined six cross-cultural basic emotions that are reflected in characteristic facial expressions: joy, anger, fear, surprise, sadness, and disgust.
empathy
The term "empathy" comes from the ancient Greek word for "passion." Today, empathy is understood as the ability to put oneself in another person's shoes and understand their feelings, thoughts, and actions. In neuroscience, empathy is supported by mirror neurons, among other things: nerve cells that show similar activity when observing an action as when performing it.
Endorphins
Abbreviation for endogenous morphines, i.e., morphines produced by the body itself. They play an important role in suppressing and alleviating pain. They are also involved in euphoria (feelings of elation).
Engram
An engram, also known as a memory trace, is a neural representation of memory content. It is believed that learning processes are based on structural changes in the synaptic connections between neurons.
Epigenetics
Biologists use the term "epigenetics" to describe all processes that influence the genetic activity of an organism without changing the sequence of DNA building blocks. This occurs, for example, when the cell chemically modifies certain sections of the genetic material, thereby permanently or temporarily deactivating them. For example, although women have two X chromosomes in every cell of their body, one of them is so tightly packed that it does not become active.
Epiphysis
The epiphysis (pineal gland) is an unpaired component of the epithalamus (part of the diencephalon). It is a gland that secretes melatonin. Among other things, the epiphysis controls the "internal clock."
Episodic memory
Episodic memory is a form of declarative long-term memory. It includes one's own biography, i.e., important experiences and events from the past, including their location in space and time, as well as the feeling of having had the experience oneself.
Epithalamus
A part of the diencephalon (midbrain) located behind the thalamus (the largest part of the midbrain). It includes the habenulae and the epiphysis, among other structures.
Executive functions
Brain research uses the term "executive functions" to describe the "higher" mental abilities of living beings. These include, for example, focused attention, planning actions, error correction, decision-making, impulse control, and emotional regulation.
Extinction
In extinction, a previously conditioned stimulus is presented several times without the originally paired reinforcement until the conditioned response subsides. For example, a dog has learned that the ringing of a bell announces food (conditioned stimulus → conditioned salivation response). In extinction, the bell is now rung several times without food following. After a few repetitions, the dog stops drooling when the bell rings: the conditioned response subsides. This decrease in response can also be detected at the synaptic level, for example, by a reduction in neurotransmitter release.
Extrapyramidal system
The extrapyramidal system refers to a series of structures in the brain that play a key role in influencing motor function but are not part of the pyramidal tract. It consists of multisynaptic neuron chains. The extrapyramidal system includes numerous nuclei such as the striatum, pallidum, nucleus ruber, and substantia nigra.
excitatory
Exciting synapses are described as excitatory when they depolarize the subsequent cell membrane and can thus lead to the formation of an action potential. An excitatory effect is usually produced by an exciting transmitter (messenger substance), such as glutamate. The opposite is an inhibitory synapse.
ear
The ear is not only the organ of hearing, but also of balance. A distinction is made between the outer ear with the auricle and external auditory canal, the middle ear with the eardrum and ossicles, and the actual hearing and balance organ, the inner ear with the cochlea and semicircular canals.
ear canal
Sound waves captured by the outer ear enter the external auditory canal and cause the eardrum at the end of the canal to vibrate.
Ear drum
A thin membrane at the end of the ear canal that vibrates when sound waves hit it. The eardrum forms the transition from the outer ear to the middle ear. It is approximately 0.1 mm thick and has a maximum diameter of 10 mm. Contrary to what its name suggests, it is funnel-shaped.
Fissure
The strong folding of the cortex (cerebral cortex) creates fissures – from the Latin: cleft. These clefts can be used to describe individual brain structures. For example, the fissura sylvii separates the temporal lobe from the frontal lobe. Less deep clefts are often referred to as sulci.
Fornix
The fornix is a nerve pathway consisting of approximately 12 million fibers that connects the hippocampus (one of the oldest structures in the brain in evolutionary terms) and subiculum with the septum and mammillary bodies.
Fovea centralis
The fovea centralis is located in the center of the macula and is the area of sharpest vision in birds and higher mammals. Its diameter in humans is approximately 1.5 mm. There are no rods in the fovea, only cones, which are interconnected to the ganglion cells in the central area of the fovea at a ratio of 1:1, resulting in very high "resolution."
frontal
An anatomical position designation – frontal means "towards the forehead," i.e., at the front.
Frontal lobe
The frontal cortex is the largest of the four lobes of the cerebral cortex and its functions are correspondingly comprehensive. The front area, known as the prefrontal cortex, is responsible for complex action planning (known as executive functions), which also shapes our personality. Its development (myelination) takes up to 30 years and even then is not yet complete. Other important components of the frontal cortex are Broca's area, which controls our ability to express ourselves linguistically, and the primary motor cortex, which sends movement impulses throughout the body.
Frontotemporal dementia
Frontotemporal dementia is a neurodegenerative disease. Unlike Alzheimer's dementia, Pick's disease usually begins before the age of 60 and initially manifests itself through changes in personality and social behavior. There are also variants that begin with speech disorders. In advanced stages, memory performance is also impaired. The physiological cause is degeneration of nerve cells in the frontal and temporal lobes of the brain. Similar to Alzheimer's disease, the aggregation of certain proteins appears to play a role in pathogenesis. However, doctors do not yet understand exactly what happens in this process and what other factors contribute to the development of Pick's disease. Today, classic Pick's disease is only a subtype of FTD in which characteristic Pick bodies can be detected in the brain.
Functional magnetic resonance imaging
Functional magnetic resonance imaging (fMRI) is a modification of MRI that allows brain activity to be measured indirectly via regional blood flow and oxygen consumption. BOLD (blood oxygen level dependent) contrast is often used, which exploits differences in the magnetic behavior of oxygen-rich and oxygen-poor blood. An increase in the BOLD signal indicates increased neural activity. fMRI provides good spatial resolution and allows detailed conclusions to be drawn about the activity of specific areas of the brain, while the temporal resolution is in the range of seconds.
Fear conditioning
The linking of a neutral stimulus to a stimulus that triggers fear – for example, first a soft sound, then a loud, frightening noise. After conditioning, the presentation of the neutral stimulus alone triggers fear.
Field of view
The area of the outside world that can be perceived when the head is held still and the gaze is straight ahead. In humans, it is approximately 180° horizontally, of which about 120°–140° is binocular; vertically, it is approximately 135°. Rabbits achieve 360° thanks to their sideways-facing eyes, although their binocular field of vision – i.e., the intersection of both eyes – only covers 30°.
Fusiform gyrus
The fusiform gyrus is located in the inferior, i.e., inner temporal lobe and plays an important role in object recognition. Facial recognition is believed to take place in the right fusiform gyrus, which is why this structure is also referred to as the fusiform face area.
Fight-or-flight response
According to Walter Cannon's theory from 1929, animals – just like humans – respond to acute threats with increased arousal. They have the choice between fight or flight. Both reactions are triggered by the same feeling of stress.
Flocculonodular lobe
The flocculonodular lobe is an antero-inferior region of the cerebellum. It comprises two structures, the nodulus (nodule) and the flocculus (flocculus). It is involved in balance and spatial orientation, as well as in stabilizing and controlling eye movements. It corresponds to the vestibulocerebellum.
Facial expressions
Five muscle groups control the visible movements on the surface of our faces – and this applies to everyone in the world. Neuroscientists emphasize universal, evolutionarily anchored reactions as the reason for this. For this reason, the basic emotions of fear, anger, disgust, sadness, surprise, and joy leave similar traces on the face everywhere, which we can usually identify reliably even in strangers.
GABA
GABA is an amino acid and the most important inhibitory neurotransmitter, which acts as a messenger in the transmission of information between neurons at their synapses.
Ganglion cell
The ganglion cell bundles the signals from the photoreceptors in the retina and transmits them via its axons (long, fiber-like extensions of a nerve cell. All of these axons together form the optic nerve.
Ganglion
Term for a cluster of nerve cell bodies in the peripheral nervous system. The term nerve node is often used because of its appearance. (Greek gágglion = knot-like)
Gap junction
A special connection between two cells that allows direct communication in the form of electrical cell coupling. Unlike most synapses, which use chemical messengers to transmit impulses, this connection is faster.
Gene
Information unit on DNA. Specialized enzymes translate the core component of a gene into ribonucleic acid (RNA). While some ribonucleic acids perform important functions in the cell themselves, others specify the order in which the cell should assemble individual amino acids into a specific protein. The gene thus provides the code for this protein. In addition, a gene also includes regulatory elements on the DNA that ensure that the gene is read exactly when the cell or organism actually needs its product.
Gesture
A nonverbal form of communication in which certain movements convey meaning – a shrug of the shoulders, a dismissive wave of the arm.
Glial cells
Glia cells are the second largest group of cells in the brain after neurons. For a long time, they were considered inactive elements of the brain, referred to as "nerve cement." Today, we know that the different types of glia cells (astrocytes, oligodendrocytes, and microglia in the CNS; Schwann cells in the PNS) perform clearly defined tasks in the nervous system. For example, they respond to pathogens, play an important role in nourishing nerve cells, and insulate nerve fibers. They account for slightly more than 50 percent of the brain's cells, compared to neurons.
Gliotransmitter
Chemical messengers released by astrocytes and other glial cells. They enable glial cells to communicate with other cells in the nervous system, for example when forming a synapse. The most common types of gliotransmitters are the amino acids glutamate and D-serine, as well as adenosine triphosphate (ATP).
Glutamate
Glutamate is an amino acid and the most important excitatory neurotransmitter, which acts as a messenger substance in the transmission of information between neurons at their synapses.
Golgi’s method
A staining method that can be used to visualize entire nerve cells. When Italian physician and scientist Camillo Golgi (1843–1926) treated nerve tissue with a solution of potassium dichromate and silver nitrate, small crystals of silver chromate formed in the cells – but only in every 10th cell. Golgi initially called his method the "black reaction." With the help of this process, it was shown that the entire nervous system consists of individual neurons.
Golgi tendon organ
The Golgi tendon organ is a sensor located at the junction between the tendon and the muscle. It reacts primarily to muscle contraction and can thus register muscle tension. This in turn provides information about the position of individual body parts in space.
Gray matter
Grey matter refers to a collection of nerve cell bodies, such as those found in nuclei or in the cortex.
Grandmother neuron
Reference to a now outdated model from learning psychology. The term was coined by Polish neurophysiologist Jerzy Konorski in the 1960s. He imagined that a specific cognitive process in the brain – such as thinking about one's grandmother – is always linked to the activity of one and the same neuron. However, scientists have since discovered that the whole process is somewhat more complicated: memories are generated by a spatial and temporal pattern of action potentials from different nerve cells.
Gustatory cortex
Here, the brain processes information from the taste receptors. When these are stimulated, the sensory cells in the taste buds send a signal to the thalamus via various intermediate stations. The thalamus then forwards this signal to the insular lobe. This is where the primary gustatory cortex is located, which combines the information from the taste pathways with other sensory impressions. The primary gustatory cortex then forwards the combined data package to its secondary counterpart. This is located in the orbitofrontal cortex, where the final processing of olfactory information also takes place.
Granule cell
Relatively small nerve cells found in the cortex (cerebral cortex), hippocampus, olfactory bulb, and cerebellum. In the cortex, they are primarily located in layer IV and are predominantly excitatory. In the cortex of the cerebellum, they constitute 99% of the cells and form the parallel fibers.
Huntington's disease
Huntington's disease is a progressive and fatal hereditary disease that manifests itself in the brain. It is characterized by dyskinesia, dementia, and behavioral and psychological changes. To date, there is no cure, although scientists have a relatively good understanding of its molecular causes. The Huntington's gene of those affected contains up to 200 copies of a specific base triplet (group of three bases). This causes the cells to produce a defective protein, which primarily forms deposits in the striatum of the brain. This leads to degeneration of the neurons in the basal ganglia and the cortex.
Hair cells
Sensory cells in the inner ear located in the organ of Corti and the semicircular canals. The hair cells in the organ of Corti are responsible for transducing (converting) the vibrations into electrical potentials. Each of these sensory cells has hair-like protrusions of varying lengths, called stereocilia. These are interconnected. The movement of these stereocilia caused by the vibrations is the key to signal transduction in the hair cells.
Habenulae
The habenulae – literally translated as "the reins" – are part of the epithalamus (which is part of the diencephalon) and are primarily involved in the modulation of monoamine neurotransmitters (dopamine, serotonin).
Habituation
If stimuli are repeatedly presented without having any effect, habituation to these stimuli occurs. This weakens the response and, over time, it disappears completely.
Hammer
The first of the small ossicles in the middle ear. It is connected to the eardrum and transmits the vibrations caused by sound waves via the other two ossicles (incus, stapes) to the cochlea, where the stimulus is converted into a neural signal.
Haptics
Haptic perception is based on the sensory cells of the skin and depth sensitivity. It is an active process that allows the shape, structure, weight, temperature, etc. of an object to be explored. Haptics is the "science of touch."
Hebbian theory
Hebbian theory is the hypothesis postulated in 1949 by Canadian psychologist Donald Hebb that the synaptic connection between two neurons is strengthened when both are active at the same time. This principle forms a cellular basis for learning and memory. "Neurons that fire together, wire together" – they form a common connection.
Hemiparesis
In medicine, hemiparesis refers to incomplete paralysis of one side of the body. It occurs as a result of damage to the central nervous system, such as that caused by a stroke. Since nerve centers in the right hemisphere of the brain control movement of the extremities on the left side of the body and vice versa, hemiparesis typically occurs on the side of the body opposite to the site of the damage.
Hemisphere
The cerebrum and cerebellum each consist of two halves – the right and left hemispheres. In the cerebrum, they are connected by three pathways (commissures). The largest commissure is the corpus callosum.
Heschl's gyrus
Heschl's gyrus is an area in the temporal lobe that was first described by Richard Heschl in 1855. It is the seat of the primary auditory cortex, i.e., the hearing center in the cerebral cortex.
Hippocampus
The hippocampus is the largest part of the archicortex and an area in the temporal lobe. It is also an important part of the limbic system. Functionally, it is involved in memory processes, but also in spatial orientation and learning. It comprises the subiculum, the dentate gyrus, and the Ammon's horn with its four fields CA1-CA4.
Changes in the structure of the hippocampus due to stress are associated with chronic pain. The hippocampus also plays an important role in the amplification of pain through anxiety.
Histology
Histology is the study of tissue. It involves examining tissue samples. The tissue is processed and stained using various methods and cut into thin sections that can be examined under a microscope.
Homo economicus
A term from economics describing the idea that people always act according to the maxim of optimizing their own utility. However, the motive is not primarily selfish, but rather rational. This view of human nature contrasts with that of Homo reciprocans, which assumes that people prioritize cooperative behavior.
Homeostasis
Homeostasis is the ability of an organism to maintain internal conditions such as metabolism, body temperature, blood pressure, etc. at a relatively constant level. The maintenance of homeostasis is controlled by the autonomic nervous system, meaning that humans cannot directly influence its regulation at will.
Homunculus
In the brain, every part of the body is represented in precisely defined locations, both sensorily and motorically. Body parts with a high density of sensory receptors (fingertips, tongue) are represented more prominently than those with a lower receptor density (back, legs). Neural maps are developed, e.g., of the hand or face. If these maps are graphically assigned to their body parts, the result is a homunculus, i.e., a small human being. The size of its respective body parts reflects their motor capabilities or sensitivity. This makes the homunculus appear strangely distorted.
Horizontal cell
Horizontal cells are nerve cells in the retina. They form a lateral connection between photoreceptors and bipolar cells. In this way, they increase the contrast of what is seen.
Hormone
Hormones are chemical messengers in the body. They serve to transmit information between organs and cells, usually slowly, e.g., to regulate blood sugar levels. Many hormones are produced in glandular cells and released into the blood. At their destination, e.g., an organ, they dock at binding sites and trigger processes inside the cell. Hormones have a broader effect than neurotransmitters; they can influence various functions in many cells of the body.
Hyperbinding
An explanatory model for the phenomenon of synesthesia. Those affected relate different aspects of perception such as shapes, colors, sounds, and smells so strongly to each other that they temporarily experience them as a single entity. To a certain extent, this "connection" occurs in all people. In synesthetes, however, it is particularly pronounced and also arises in areas of the perceptual spectrum that most people would not associate with each other.
Hypercomplex cell
A nerve cell in the primary visual cortex that responds most strongly to short, moving lines or corners in its receptive field. It exhibits end-stopping, meaning that the response strength decreases when the stimulus becomes longer than optimal. Hypercomplex cells are sensitive to the orientation and direction of movement of the stimulus and contribute to the perception of edges, corners, and curves.
Hypophysis
The pituitary gland is an important hormone gland in the body. It hangs like a drop below the hypothalamus and is no larger than a pea. The pituitary gland consists of two parts, the anterior lobe (adenohypophysis) and the posterior lobe (neurohypophysis). The anterior lobe of the pituitary gland has the special property of being partially exempt from the blood-brain barrier, allowing it to release hormones directly into the blood.
Hypothalamus
The hypothalamus is considered the center of the autonomic nervous system, meaning it controls many motivational states and regulates vegetative aspects such as hunger, thirst, and sexual behavior. As an endocrine gland (which, unlike an exocrine gland, releases its hormones directly into the blood without a duct), it produces numerous hormones, some of which inhibit or stimulate the pituitary gland to release hormones into the blood.In this function, it also plays an important role in the response to pain and is involved in pain modulation.
Inferior colliculus
Two posterior elevations of the midbrain roof are referred to as the inferior colliculi. Together with the superior colliculi, they form the midbrain tectum. Impulses from various nuclei of the lower brain stem converge at the inferior colliculi. In addition, signals from the auditory cortex arrive here. This makes the inferior colliculi an important coordination center for auditory information.
Inhibition
Neuronal inhibition describes the phenomenon whereby a sender neuron sends an impulse to a receiver neuron, causing the latter's activity to decrease. The most important inhibitory neurotransmitter is GABA.
Iconic memory
An ultra-short-term memory for visual content. This is absorbed passively and overwritten after less than a second.
inferior
An anatomical position designation – inferior means located further down, the lower part.
Inferior occipital gyrus
Part of the occipital lobe, the rearmost of the four large lobes of the cerebral cortex. Functionally, this is where visual information is processed. The inferior occipital gyrus is part of the early visual association areas.
Inhibiting hormones
Hormones produced in the hypothalamus that inhibit the release of other hormones from the adenohypophysis (part of the pituitary gland).
Inner hair cell
Outer and inner hair cells are sensory cells for acoustic signals in the organ of Corti. At their tips, they have hair-like projections called stereocilia, which are interconnected.
The approximately 3,000 inner hair cells are all arranged in a row. They are the actual acoustic sensory cells. The stereocilia are deflected by fluid movement in the subtectorial cleft.
Insula
The insula is a recessed part of the cortex (cerebral cortex) that is covered by the frontal, temporal, and parietal lobes. This overlay is called the opercula (lid). The insula influences the motor and sensory functions of the intestines and is considered to be the link between cognitive and emotional elements in pain processing. It is also involved in processes such as taste and physical self-awareness.
Intelligence
Collective term for human cognitive performance. According to British psychologist Charles Spearman, cognitive performance in different areas correlates with a general factor (g factor) of intelligence. This means that intelligence can be expressed as a single value. American psychologist Howard Gardner, among others, has developed a counter-concept to this, known as the "theory of multiple intelligences." According to this theory, intelligence develops independently in the following eight areas: linguistic, logical-mathematical, musical-rhythmic, visual-spatial, bodily-kinesthetic, naturalistic, intrapersonal, and interpersonal.
Intelligence quotient
A measure intended to express a person's intellectual capacity. Tests designed to determine intelligence are based on the concept that there is a general factor of intelligence that is normally distributed across the population. The first IQ tests were developed in the early 20th century by Alfred Binet, who wanted to use them to determine the relative intelligence age of schoolchildren. According to his definition, IQ is the quotient of intelligence age and chronological age multiplied by 100. This is also the average IQ of a person. Modern tests often use standard deviations for normalization, which means that IQ is still scaled to average = 100, SD = 15, without directly calculating intelligence age. 95 percent of the population has IQ scores between 70 and 130. If someone scores below 70, they are considered to have intellectual disability, while a score above 130 is considered gifted.
Interneurons
A small multipolar neuron that is neither sensory nor motor, connected between two other neurons and conducting impulses from one nerve cell to another. In the central nervous system, interneurons are mostly inhibitory and use the neurotransmitters GABA and glycine.
Ion channel
Ion channels are embedded in the cell membrane of nerve cells and all other cells in the body. They enable electrically charged particles, known as ions, to pass through the cell membrane into and out of the cell. They can therefore influence the membrane potential of a cell and trigger an action potential. A large number of different ion channels are known. Normally, ion channels have a specific permeability for only one type of ion, e.g., sodium ions or potassium ions. These are referred to as sodium channels or potassium channels, respectively.
ipsilateral
Ipsilateral is a positional term. It means "located on the same side of the body."
Iris
The (German) name "rainbow membrane" refers to the pigment coloration of the iris. Its size changes depending on the brightness of the surroundings, and with it the size of the pupil.
Infundibular nucleus
The infundibular nucleus is also called the arcuate nucleus due to its curved shape. It is located in the hypothalamus at the base of the third ventricle and regulates hormone release from the pituitary gland via releasing and inhibiting hormones. It is therefore also involved in regulating appetite, energy balance, and growth.
Inferior olivary nucleus
The inferior olive – more precisely, the olive nucleus complex – is one of the largest nucleus complexes in the brain stem. It plays an important role in fine-tuning motor skills, as it forms the connection between the motor cortex and the cerebellum.
James-Lange theory
A theory of emotion developed by William James and (independently) Carl Lange in 1884, which assumes that emotions go through a kind of loop before they become conscious: the brain processes sensory signals, to which it responds by causing changes in the organism. It is only on the basis of these physical processes that the emotion becomes conscious. For example, the heart beats faster, which promotes the emotion of fear.
Jennifer Aniston neuron
The neuroscientific granddaughter of the grandmother neuron: In 2005, Rodrigo Quian Quiroga and his team discovered nerve cells in the temporal lobe of epilepsy patients that reacted specifically to certain objects – such as a picture of actress Jennifer Aniston. The angle from which the photos were taken was irrelevant. These neurons are part of a network of neurons that together represent a concept. However, there are strong indications that these cells are responsible not only for a single concept, but for several.
Lateral geniculate body
The lateral geniculate nucleus is the section of the thalamus (the largest part of the diencephalon) where around 90% of the optic nerve axons terminate. It has a characteristic stratification into six cell layers. The nerve cells of the lateral geniculate nucleus send their projections to the visual cortex. Together with the medial geniculate nucleus, it forms the metathalamus.
Long-term memory
Long-term memory stores information about events, facts, or skills over long periods of time, often for a lifetime. Different types of memory are stored in different areas of the brain. The cellular basis for these learning processes is based, among other things, on improved communication between two cells and is called long-term potentiation.
Long-term potentiation
Long-term potentiation is a central mechanism for learning and memory formation. It is based on improved communication between two cells, referred to as strengthening the connection. This strengthening can occur, for example, through an enlargement of the connection point, the installation of new channels, or an increased release of transmitters (messenger substances).
Lesion
A lesion is damage to organic tissue.
lateral
A positional term – lateral means "towards the side." In relation to the nervous system, it refers to a direction at right angles to the neural axis, i.e., to the right or left.
Lateral inhibition
Lateral inhibition is a principle of neural stimulus processing, according to which the retina, among other things, is structured. There, the nerve cells of an area are interconnected in such a way that when they are excited, they inhibit the activity of the surrounding neurons.
Lewy body dementia
A neurodegenerative disease that resembles Alzheimer's disease, but also Parkinson's disease in its symptoms. The Lewy bodies that give the disease its name are caused by protein deposits in the nerve cells of the cerebral cortex and brain stem, which impair the function of the corresponding neurons. In addition to cognitive impairment, Lewy body dementia often causes hallucinations or depression, as well as changes in mobility similar to those seen in Parkinson's disease.
Limbic cortex
The limbic cortex primarily comprises the cingulate gyrus and adjacent structures such as the entorhinal cortex. It is part of the limbic system, which also includes regions such as the hippocampus and the amygdala. The limbic system plays a central role in processing emotions, motivation, and instinctive behavior.
Limbic system
The limbic system is a functional unit in the brain. It consists of interconnected structures, primarily in the cerebrum and diencephalon. The structures assigned to the system vary depending on the source, but the most important components are the hippocampus, amygdala, cingulate gyrus, septum, and mammillary bodies. The limbic system is involved in autonomic and visceral processes as well as in mechanisms of emotion, memory, and learning. Some authors mistakenly reduce the limbic system to the emotional world by referring to it as the "emotional brain."
Lens
The eye lens is a transparent, flexible structure which, thanks to its varying degree of curvature (see ciliary muscle and zonular fibers), enables the process of accommodation (focusing) and thus sharp vision at different distances, especially at close range.
Lucid dream
During a lucid dream, the dreamer is aware of their state and able to control their actions. Although Aristotle reported on this phenomenon and up to 80 percent of all people say they have had lucid dreams, sleep researchers doubted the existence of this phenomenon until the end of the 1960s. Most observations of lucid dreams originate from the REM sleep phase. Scientists have found that lucid dreams are associated with altered activity in the prefrontal cortex, which is responsible for the critical evaluation of events. Lucid dreaming can be learned and is now also used in therapy, for example in the treatment of nightmares.
Lateral nucleus
The lateral nucleus belongs to the basolateral nucleus group of the amygdala. The basolateral amygdala is the largest part of the amygdala. It receives sensory information from the temporal lobe and neuromodulatory signals from the VTA, locus coeruleus, and basal forebrain, processes them, and sends them to the central nucleus. It is important for emotional learning and fear conditioning.
Lock and key
In terms of the processes in a synapse, this means that the chemical messenger and its receptor must fit together like a key in a lock. The receptor therefore only "accepts" a very specific messenger.
Mamillary bodies
Two structures of the posterior thalamus (largest part of the diencephalon). Due to their similarity to the female breast, they are also called mammillary bodies. They are located at the front end of the fornix and are attributed to the limbic system.
Medial geniculate body
The medial geniculate body (medial geniculate nucleus) is a nucleus of the thalamus (the largest part of the diencephalon). As the central switching point of the auditory pathway, it transmits impulses from the inferior colliculus to the auditory radiation. Together with the lateral geniculate body, it forms the metathalamus.
Misattribution
Mismatch refers to an incorrect attribution of cause, for example between physical experience and cognitive evaluation. In an experiment conducted by Dutton and Aron (1974), male subjects were placed in a risky situation, which caused intense physical arousal. At the end of the experiment, the men were interviewed by an attractive woman. Two-thirds of the test subjects later called the woman – they had misattributed their arousal caused by the risk to romantic feelings.
Memory
Memory is a generic term for all types of information storage in the organism. In addition to pure retention, this also includes the absorption of information, its organization, and retrieval.
Macula
The area of the retina with the highest density of photoreceptors. Due to this high "resolution," we see very sharply here. The diameter of the macula in humans is approximately 5 mm. The fovea centralis is located in the center of the macula.
Magnetic resonance imaging
A device used by medical professionals for magnetic resonance imaging (MRI). MRI is an imaging technique used to diagnose malformations in various tissues or organs of the body. This method is particularly effective for imaging parts of the body that contain a lot of water. Patients are placed in a tube (scanner) and exposed to a strong magnetic field. However, they are not exposed to X-rays or other forms of ionizing radiation.
Method of loci
A method of memorization in which individual pieces of information – from a lecture, for example – are assigned to specific locations along a familiar route. To recall the information during the lecture, this route is mentally retraced and the information is presented in the corresponding order.
Macular organs
Together with the semicircular canals, the macular organs form the vestibular system in the inner ear of vertebrates. They consist of two structures positioned perpendicular to each other, the saccule and the utricle. This alignment enables the macular organs to perceive linear accelerations of the body in space along all three spatial axes: up-down, front-back, left and right.
Magnetic resonance imaging
An imaging technique used by doctors to diagnose various diseases and malformations in different tissues or organs of the body. It is based on the fact that the nuclei of some atoms have an intrinsic angular momentum that aligns itself in a strong magnetic field. This property applies to hydrogen, among other elements. This is why tissues that contain a lot of water can be visualized particularly well. Abbreviation: MRI.
Manic
A mental disorder characterized by changes in mood. Manic individuals are extremely restless. Symptoms can also include excessive self-confidence, compulsive talking, reduced need for sleep, and impulsiveness. Mania most commonly manifests as part of bipolar disorder, in which manic and depressive phases alternate. This clinical picture is associated with an imbalance of various neurotransmitters in the brain. Accordingly, psychiatrists often treat mania with neuroleptics, which are designed to weaken the effect of neurotransmitters.
mechanoreceptor
Mechanoreceptors are sensors that respond specifically to pressure, touch, vibration, or stretching. They are found in the skin, but also in muscles and tendons, and are specialized for different stimuli.
medial
A positional term – medial means "towards the middle." In relation to the nervous system, it refers to a direction toward the body, away from the sides.
Medial orbitofrontal cortex
The ventral (in humans, "lower") middle part of the frontal lobe. This part of the cortex influences complex mental processes such as planning, reward evaluation, and decision-making. Patients with lesions in the frontal lobe show personality changes and are often no longer able to control their impulses.
Medial temporal lobe
The medial part of the temporal lobe contains the hippocampus and a number of other anatomically related structures: the entorhinal, perirhinal, and parahippocampal cortex. Together, they enable us to consciously remember facts and events. This region of the brain is also important for the formation of long-term memory. Deep inside the medial temporal lobe is the amygdala, which is involved in emotion processing, emotional salience, and emotional reinforcement of memories.
Medulla oblongata
Area of the brain that transitions into the spinal cord. The medulla oblongata comprises nerve pathways between the spinal cord and higher brain regions, as well as numerous core areas with functions that are in some cases vital, such as breathing, heartbeat, and certain reflexes.
Meissner’s corpuscles
Meissner’s corpuscles are a type of mechanoreceptor found in hairless skin, such as that on the fingertips. Meissner corpuscles respond to vibration, pressure, and touch.
Melatonin
Melatonin is a hormone released by the pineal gland in the brain when it is dark. Melatonin levels are highest at night and then decrease throughout the day. This makes it an important messenger substance for the "internal clock" and it appears to play a particularly important role in regulating sleep.
Membrane potential
The membrane potential is a voltage measured between the inside and outside of the cell membrane. It arises from the different distribution of electrically charged particles inside and outside the cell.
Mental training
Originally a concept from sports psychology: athletes imagine movement sequences and optimize them in their minds. Although comparable methods are now also used in other areas of life, the effectiveness of mental training has been most thoroughly researched in athletes. According to research findings, mental imagery actually changes the brain. This works because imagining movement sequences activates similar areas of the brain as during actual training.
Merkel cells
Merkel cells are slow-adapting mechanoreceptors in the skin. They respond to continuous pressure and are important for the perception of shape, edges, and fine details.
Midbrain
The midbrain is the uppermost section of the brain stem. Its regions are located around the aqueduct, a canal filled with cerebrospinal fluid. Prominent structures include the tectum, tegmentum, and substantia nigra.
Mesolimbic pathway
A system of neurons that use dopamine as a neurotransmitter and play a crucial role in emotion, reward, and substance abuse. The cell bodies are located in the subtegmental area and extend to the amygdala, the hippocampus, and – most importantly – the nucleus accumbens, where they have their terminal buttons.
Migraine with aura
The symptoms at the onset of a classic migraine attack. About one in five migraine attacks is preceded by characteristic perceptual disturbances, such as patients only being able to see part of their field of vision or seeing blurry. These symptoms usually come on slowly and also disappear slowly. This does not cause any damage to the brain tissue.
Microexpressions
Microexpressions are facial expressions that last only a fraction of a second. They cannot be consciously controlled and are rarely consciously perceived by others.
Microglia
The smallest type of glial cell is part of the cellular immune system and is responsible, among other things, for removing dead neurons. Microglia can move in an amoeba-like manner.
Microtubules
Microtubules are one of the main components of the cytoskeleton, which gives cells stability and support. They consist of many copies of the proteins alpha- and beta-tubulin, which pair up to form tubes with a diameter of 20 to 30 nanometers. In addition to their supporting function, microtubules play an important role in transporting messenger substances through the cell. In neurons, for example, vesicles filled with neurotransmitters move along them to the synapses. In the nerve cells of the brains of Alzheimer's patients, a protein called tau can no longer stabilize the microtubules properly. As a result, they disintegrate, which contributes significantly to the development of dementia.
Mitochondria
Mitochondria are organelles inside a cell. They are also referred to as the "powerhouse" of cells because they supply them with energy. They have their own DNA, which is only inherited from the mother.
Middle ear
The eardrum forms the boundary between the outer ear and the middle ear. The ossicles – the malleus, incus, and stapes – transmit the vibration of the eardrum to the inner ear via the oval window. The middle ear is filled with air.
Mnemonics
Mnemonics is a collective term for methods that facilitate the learning of new content. The simplest mnemonic device is the memory aid.
Mossy fiber
Mossy fibers are nerve fibers that conduct impulses from the spinal cord and the pontine nuclei to the cerebellum. There they terminate in the granule cell layer. The axons of the granule cells of the dentate gyrus in the hippocampus, which extend to CA3, are also referred to as mossy fibers.
Morphine
Depending on the dose, morphine is either a potent painkiller or a mind-altering drug. Synthesized from poppy seeds and named after the Greek god of dreams, morphine binds to the opioid receptors in the brain.
Motivation
A motive is a reason. When this motive takes effect, the living being feels motivation – it strives to satisfy its need. For example, for food, protection, or reproduction. Motivation can be intrinsic (from within, e.g., curiosity) or extrinsic (from outside, e.g., reward).
Motor neuron
Neurons that extend from the central nervous system to the muscles and control their activity.
Multiple sclerosis
A common neurological disease that predominantly occurs in young adults. For reasons that are still unclear, the body's own cells attack and destroy the myelin sheaths of nerve cells. This can happen throughout the central nervous system, which is why two different multiple sclerosis patients can suffer from very different symptoms. Common symptoms include visual disturbances, numbness in the arms and legs, but also coordination problems, muscle weakness, and bladder problems.
Myelin
Myelin is a fatty substance produced by glial cells. It envelops the axons (long, fiber-like extensions) of nerve cells and insulates them, preventing messages from passing uncontrollably to neighboring nerve cells. This also greatly accelerates conduction velocity.
Medial nuclei
The medial thalamic nuclei, especially the mediodorsal nucleus, are located in the medial thalamus and are closely connected to the prefrontal cortex and the limbic system. They are primarily responsible for higher cognitive functions such as planning, attention, and working memory, but are also involved in processing emotions and motivation. In addition, they integrate complex information from different areas of the brain.
Mirror neurons
Nerve cells in the brains of primates that fire just as strongly when their owners observe an action as when they perform it themselves. Italian researchers discovered these special neurons in the early 1990s while experimenting with macaques. Mirror neurons were later also detected in the human brain. Among other places, they occur in Broca's area, which is responsible for language processing. Mirror neurons could provide an explanation for why we are able to understand the feelings and intentions of others. The discussion on this topic is still ongoing.
Nucleus
In cell biology, the nucleus in a cell is the cell nucleus, which contains the chromosomes, among other things. In neuroanatomy, the nucleus in the nervous system refers to a collection of cell bodies – known as gray matter in the central nervous system and ganglia in the peripheral nervous system.
Nose
The olfactory organ of vertebrates. In the nasal cavity, the air is cleaned by cilia, and in the upper area is the olfactory epithelium, which detects odors.
neglect
Neglect is a perceptual disorder in which parts of the body or stimuli are ignored due to a brain lesion. The disorder affects the sides opposite the brain lesion. It usually occurs after lesions in the right parietal lobe. Accordingly, visual, auditory, and somatosensory stimuli on the left side are ignored.
Neocortex
The neocortex is the phylogenetically youngest part of the cerebral cortex. Since it is structured relatively uniformly in six layers, it is also referred to as the isocortex.
Neurodegeneration
Collective term for diseases in which nerve cells gradually lose their structure or function until they eventually die. In many cases, misfolded proteins are the trigger – such as certain forms of the proteins beta-amyloid and tau in the case of Alzheimer's disease. In other diseases, such as Parkinson's disease or Huntington's disease, proteins within the neurons are not broken down properly. As a result, toxic aggregates are deposited there, leading to the respective disease symptoms. While Huntington's disease is clearly genetic, in Parkinson's and Alzheimer's there appear to be certain gene variants that promote their development. None of these neurodegenerative diseases can be cured at present.
Neuroenhancement
Neuroenhancement is about improving cognitive performance. To this end, drugs used to treat dementia, hyperactivity, or narcolepsy are taken by healthy individuals with the aim of improving their learning abilities, increasing their alertness, or staying awake and active for longer. In addition to the ethical questions this raises, there is also medical controversy as to whether this self-medication actually works and what the long-term consequences might be.
Neurofibrils
Neurofibrils are fine fibrous structures in nerve cells that consist mainly of neurofilaments (a form of intermediate filaments) and other components of the cytoskeleton. They run in bundles through the cell body and the extensions of neurons and contribute significantly to the stabilization and shaping of the nerve cell. They appear as characteristic features of neurons even in the early embryo.
Alzheimer's disease causes profound changes in cytoskeletal structures: the protein tau, which normally stabilizes microtubules, becomes excessively phosphorylated, detaches from the microtubules, and aggregates to form the typical neurofibrillary tangles (fibrillary bundles). These are a central pathological feature of the disease.
Neurohypophysis
The neurohypophysis is the posterior lobe of the pituitary gland. It stores the hormones oxytocin and vasopressin, which are produced in the hypothalamus, and releases them into the bloodstream when needed.
Neuromarketing
A relatively new, interdisciplinary field of research in market research that builds on the findings of neuroeconomics – and is not entirely without controversy. The concept of neuromarketing is based on the assumption that customers make purchasing decisions primarily on the basis of unconscious emotional reactions. Neuromarketing uses neurophysiological measurement methods to study these reactions in order to better understand how consumers respond to products, advertising, and sales environments – with the aim of influencing these responses and thus purchasing decisions at the point of sale (the store) through measures such as music or scents.
Neuron
A neuron is a specialized cell in the nervous system that is responsible for processing and transmitting information. It receives signals via its dendrites and transmits them via its axon. Transmission occurs electrically within the neuron and, between neurons, usually chemically via synapses.
Neural representation
Various parts of the brain contain representations not only of the sensory systems, but also of objects such as faces. For example, so-called place cells in the hippocampus appear to play an important role in the representation of space. Each place cell represents a specific location in the environment and becomes active when its owner is at that location. Another group of neurons, grid cells, fire in a regular hexagonal pattern that is interpreted as a metric grid of the environment. This grid provides a kind of coordinate system that place cells can use for location coding.
Neuron doctrine
The neuron doctrine forms the basis for our current understanding of the nervous system. According to this doctrine, the brain does not consist of a single, interconnected nerve network, but rather of individual nerve cells that communicate with each other via contact points. This was discovered by the Spanish Ramon y Cajal at the end of the 19th century when he stained nerve cell preparations from chickens and mammals. He used a staining technique developed by Camillo Golgi. For their achievement, the two researchers – who were unfortunately at odds with each other – were awarded the Nobel Prize in Medicine in 1906.
Neuroeconomics
Term for a field of research at the interface between neuroscience, economics, and psychology. The overarching goal of neuroeconomics is to understand how people make economic decisions. To this end, neuroeconomists investigate what happens in the brain during decision-making. They often use experimental setups from game theory, which usually involve winning or losing money. They examine the brains of their test subjects primarily using imaging techniques. Neuroeconomics is a young branch of research that is attracting great social interest.
Neurotransmitter
A neurotransmitter is a chemical messenger, an intermediary substance. It is released by the sender neuron at the sites of cell-cell communication and has an excitatory or inhibitory effect on the receiver neuron.
NMDA receptor
NMDA receptors are specialized receptor channels in the membrane of nerve cells that only open under very specific conditions. First, the neurotransmitter glutamate must bind to the receptor, and second, the receptor needs a cofactor such as glycine or D-serine. In addition, the postsynaptic cell membrane must be depolarized so that the magnesium ion (Mg²⁺) normally located in the channel pore is removed. If these conditions are met, an ion channel opens in the center of the receptor and allows calcium ions (Ca²⁺) in particular, but also sodium ions (Na⁺), to flow into the cell, while potassium ions (K⁺) flow out of the cell. The cell can respond to the influx of calcium in a variety of ways. NMDA receptors enable the brain to modify synaptic connections throughout life. They are crucial for forms of synaptic plasticity such as long-term potentiation (LTP) and long-term depression (LTD) and thus play a central role in the formation and storage of memory content.
Non-declarative memory
Non-declarative memory is part of long-term memory. It encompasses automated behaviors, learned skills, and habits that usually occur unconsciously. In contrast to declarative memory, the contents of non-declarative memory are difficult or impossible to express verbally. Non-declarative memory includes procedural learning and priming, among other things.
Norepinephrine
Along with dopamine and adrenaline, norepinephrine (NE) or sometimes noradrenaline (NA)belongs to the catecholamines. It is produced in cells of the locus coeruleus and in the adrenal medulla and usually has a stimulating effect. Noradrenaline is often associated with stress.
Nociceptor
Nociceptors are the pain receptors in the body. They respond to sharp stimuli, heat, or chemical stimuli such as acid.
In other words, they respond to imminent or actual tissue damage. Noxiceptors are found in almost all tissues in the human body – with one important exception: the brain itself, whose nerve tissue does not contain any noxiceptors.
Nucleus
Nucleus, plural nuclei, has two meanings: in cell biology, it refers to the cell nucleus, which contains chromosomes, among other things. In neuroanatomy, it refers to a collection of cell bodies in the nervous system – in the central nervous system as gray matter, in the peripheral nervous system as ganglia.
Nucleus accumbens
The nucleus accumbens is a nucleus in the basal ganglia that receives dopaminergic (dopamine-responsive) inputs from the ventral tegmental area. It is associated with reward and attention, but also with addiction. In pain processing, it is involved in motivational aspects of pain (reward, pain reduction) and in the effect of placebos.
Nucleus tractus solitarius
A nucleus in the medulla oblongata that serves as an important integration center for visceral information. Among other things, it processes taste stimuli (via nerves VII, IX, and X) and transmits them via the thalamus (ventral posteromedial nucleus, VPM) to the primary gustatory cortex. The NTS is also involved in the motor functions of swallowing, coughing, and respiratory control by transmitting signals to motor nuclei such as the nucleus ambiguus. These reflexes serve to protect the respiratory tract and facilitate food intake.
Nonspecific Thalamus
The "non-specific" thalamic nuclei, which have only a few connections to the cortex that are not limited to a specific area, are collectively referred to as the nonspecific thalamus and sometimes truncothalamus. It receives inputs from the reticular formation, the basal ganglia, and the cerebellum. Efferences go to most of the other thalamic nuclei.
Outer hair cell
Outer and inner hair cells are sensory cells for acoustic signals in the organ of Corti. At their tips, they have hair-like projections called stereocilia, which are connected to each other and, in the case of the outer hair cells, also to the tectorial membrane. The three rows of outer hair cells filter acoustic signals and act as a cochlear amplifier: without them, our hearing sensitivity would be reduced by about 50 dB.
Olfactory bulb
The anterior part of the brain that transmits information from the olfactory nerves to the olfactory brain (rhinencephalon) after initial processing via the olfactory tract.
Optic chiasm
The optic chiasm is a cross-shaped junction between the optic nerves, where 50% of the optic nerve fibers change sides.
Ossicles
The three bones located in the middle ear – the stapes, malleus, and incus – are known as the ossicles. These are the smallest bones in the human body. They mechanically transmit sound waves from the eardrum to the cochlea.
Olfactory epithelium
An area of olfactory cells measuring approximately 5 cm² located at the rear of the nasal septum. The axons (long, fiber-like extensions of nerve cells) of the olfactory cells form the olfactory nerve and travel through the ethmoid bone to the olfactory bulb.
Occipital lobe
One of the four large lobes of the cerebral cortex. The occipital lobe lies above the cerebellum. It borders the parietal and temporal lobes at the front. The calcarine sulcus divides the occipital lobe into an upper and lower half, the cuneus and the lingual gyrus. Functionally, this area of the brain is responsible for the central processing of visual information – both the primary and secondary visual cortex are located in the occipital lobe.
Olfactory cortex
The olfactory cortex comprises the structures of the cerebrum that are responsible for processing olfactory information. The primary olfactory cortex is the prepiriform cortex, an evolutionarily ancient part of the cortex (paleocortex) with a three-layer structure.
Oligodendrocytes
Cells of the central nervous system that form the myelin sheath around nerve cells, thereby increasing their conduction velocity. They belong to the glial cells.
Oligomer
Chemists define an oligomer as a molecule composed of several structurally similar or identical units. Typically, an oligomer consists of a few monomers (e.g., 2–10, occasionally up to about 30). An example from biochemistry is collagen, which is composed of three identical polypeptide chains and occurs as a trimeric protein in connective tissue. If the number of building blocks significantly exceeds this range, as is the case with DNA, it is referred to as a polymer. Oligomers of beta-amyloid may play an important role in the development of Alzheimer's disease.
Olivary bodies
The olivary bodies are two oval structures in the lower part of the brain stem that contain clusters of nerve cell bodies. The lower olive connects the cerebrum to the cerebellum and plays an important role in controlling motor function. The upper olive is part of the auditory pathway. Its neurons can evaluate differences in transit time and level between the right and left ears, thus helping to determine the direction of sound sources.
Ontogeny
Development of an individual from a fertilized egg cell to an adult organism.
Operant conditioning
Operant conditioning refers to the influence of a behavior on display through a result of that behavior, e.g., through immediate reward or immediate punishment. Depending on the outcome, the same behavior or a different behavior will be displayed the next time.
Operculum
Cortical areas of the frontal, temporal, and parietal lobes at the lateral sulcus. The operculum covers the insular cortex.
Opsin
Opsins are light-sensitive proteins in the retina that, together with the chromophore retinal, absorb light and convert it into electrical signals. The following opsins occur in humans: rhodopsin in rods, for twilight vision, S-opsin → short-wave cones (blue), M-opsin → medium-wave cones (green), L-opsin → long-wave cones (red). These three cone opsins enable color vision.
Orbitofrontal cortex
A convolution in the orbitofrontal cortex of the cerebral cortex, located anatomically behind the eyes. The orbitofrontal cortex plays a crucial role in decision-making and monitoring social interactions and is correspondingly complex in structure. It consists of four different substructures: the medial, lateral, anterior, and posterior orbital gyri, as well as the rectus gyrus.
Oscillation
Oscillations occur when many neurons fire in synchronized, rhythmic patterns. These phased fluctuations in neural activity form the basis for measurable signals in the EEG. They reflect the coordinated processing of information in the brain.
oxytocin
Oxytocin is a hormone produced in the paraventricular nucleus and supraoptic nucleus of the hypothalamus and released into the blood via the posterior lobe of the pituitary gland. It initiates contractions during childbirth and supports the milk ejection reflex during breastfeeding. It is also released during orgasm. Oxytocin can promote trust and strengthen pair bonding, but recent findings show that its effects are more complex and, in certain contexts, can also promote separation from out-groups.
Optic nerve
The axons (long fiber-like extensions) of the retinal ganglion cells form the optic nerve, which leaves the eye at the back of the optic disc. It comprises approximately one million axons and has a diameter of approximately seven millimeters.
Optic tract
The optic tract refers to the optic nerve after half of the fibers have crossed sides at the optic chiasm. However, it still consists of the axons (long fiber-like extensions) of the retinal ganglion cells. Most of the optic tract ends in the lateral geniculate nucleus, while others end in the superior colliculi, among other places.
Olfactory tract
Smell information travels via the olfactory tract from the olfactory bulb, located just above the nose, to the primary olfactory cortex.
Olfactory trigone
At the trigonum olfactorium, the tractus olfactorius divides – forming a triangle – into the stria olfactoria lateralis and medialis.
Obsessive-compulsive disorders
This term summarizes neuropsychiatric disorders that manifest themselves in the form of obsessive thoughts on the one hand and compulsive actions on the other. For example, those affected have the urge to devote themselves to constantly recurring, mostly anxious thoughts, to wash themselves excessively often or to control their fellow human beings disproportionately. While neuroscientists used to try to explain OCD in purely psychological terms, it is now believed that some biological factors also contribute to its development, such as a disturbed metabolism of various neurotransmitters in the brain.
Praepiriform area
The praepiriform area is part of the piriform cortex in the ventral temporal lobe and belongs to the primary olfactory cortex, i.e., the primary olfactory cortex. Among other things, it contains inputs from the olfactory bulb (bulbus olfactorius) and is therefore involved in the initial cortical processing of olfactory stimuli.
Protein synthesis
The process by which cells translate units of information on DNA into functional carriers in the form of proteins. According to the central dogma of molecular biology, this process consists of two phases: During transcription, a section of genetic material is transcribed into mRNA. This tells the cell the sequence in which it should assemble individual amino acids into a protein. This happens during translation. After translation, some proteins still need to be folded or modified in other ways before they can be used as structural proteins or enzymes.
Photopigment
Photopigments are light-sensitive molecules in the receptors of the retina. When photons (particles of light) strike the photopigment, it isomerizes, triggering a cascade of various processes. In this way, light is converted into a nerve impulse. All rods have the same type of photopigment, while the cones have one of three possible photopigments.
Photoreceptors
Photoreceptors are the light-sensitive cells of the retina; they convert light into electrical potentials. There are approximately 127 million photoreceptors in the retina, including seven million cones and 120 million rods.
Pallidum
The globus pallidus, also known as the pallidum, is an important nucleus of the basal ganglia. It is a motor nucleus of the extrapyramidal system involved in the regulation of movement. The pallidum has an inhibitory and an excitatory part. The Latin name pallidus – pale – refers to the color of this nucleus.
Parahippocampal gyrus
The parahippocampal gyrus runs along the hippocampus in the lower, inner temporal lobe. Its anterior part is covered by the entorhinal cortex. It is connected to numerous areas of the cerebral cortex and projects to the hippocampus, which it also acts as a gateway to. This means that it is involved in the consolidation of explicit memory content, among other things. In addition, the posterior part of the parahippocampal gyrus contains the parahippocampal place area (PPA), which responds particularly to complex visual scenes such as rooms, landscapes, or streets and thus plays an important role in spatial orientation and location recognition.
Parkinson's disease
Parkinson's disease is one of the most common neurological disorders, caused by the death of dopamine-producing neurons in the substantia nigra, leading to a neurotransmitter imbalance in the basal ganglia. Symptoms usually begin late in life with mild tremors (resting tremor), increasing stiffness of the limbs, and slowed voluntary movements (bradykinesia). Later, postural instability, balance disorders, and difficulty walking occur. Other typical features include rigid facial expressions (hypomimia), a shuffling gait, and muscle stiffness (rigor). The disease is incurable, but its symptoms can be treated with medication (e.g., L-dopa, dopamine agonists) or surgery involving deep brain stimulation (brain pacemaker).
Paraventricular nucleus
A nucleus of the hypothalamus whose neurons produce various hormones, including oxytocin and vasopressin, which are transported to the neurohypophysis. The PVN sends axons to the limbic system, the brain stem, and other hypothalamic nuclei.
Posterior ventral nucleus
A nucleus of the dorsal thalamus that serves as the main somatosensory thalamic nucleus. The VPL receives somatosensory afferents from the body via the spinal cord (pressure, touch, vibration, proprioception, pain, temperature), while the VPM receives afferents from the head region via the trigeminal nerve. It transmits this information to the primary somatosensory cortex (S1) and thus plays a central role in the awareness of somatosensory stimuli, including pain.
Place cells
Pyramidal cells in the hippocampus that encode a specific location in a specific environment – for example, a section of a maze. When a test animal is in the center of this area, the cell fires most strongly. Place cells were discovered in 1971 by John O'Keefe and Jonathon Dostrovsky.
Paleocortex
The paleocortex is a phylogenetically very old part of the telencephalon, which together with the olfactory bulb forms the olfactory brain. The paleocortex differs from the isocortex in that it does not have a six-layer structure.
Pallidum
The "pale nucleus" (pallidum = pale) is classified as part of the basal ganglia due to its functional integration and, in terms of evolutionary development, belongs to the telencephalon. It has an inner (medial) and an outer (lateral) segment, which mainly transmit inhibitory impulses to modulate the activity of other parts of the basal ganglia and thalamus.
Papilla
The optic nerve leaves the eye at the papilla, the optic disc. Since there are no photoreceptors at this point on the retina, the optic disc creates a blind spot.
Parahippocampal cortex
The parahippocampal cortex is located next to the hippocampus and is part of the temporal lobe. It processes spatial-visual memory content and appears to be involved in the consolidation of memory content. It receives inputs from numerous polymodal cortical areas, and its outputs go to the hippocampus, amygdala, and striatum.
Paralimbic cortex
Collective term for all areas of the brain that are closely connected to the limbic system. Anatomically, the orbitofrontal cortex, cingulate gyrus, and insula belong to the paralimbic system, which plays a crucial role in mediating intense emotions. This is particularly true for feelings of fear. Neurologists often find abnormalities in the paralimbic system in the brains of psychopaths.
Parallel fiber
Parallel fibers are the axons (long fiber-like extensions) of the granule cells in the granular layer of the cerebellar hemispheres. They are so named because they run along the cerebellar gyri. They form synapses with the Purkinje cells.
Parasocial interaction
A one-sided emotional relationship with a person or fictional character with whom there is no interaction in the real world. Movie and sports stars, characters in novels, AIs or even deceased individuals can be the subject of parasocial relationships. The phenomenon itself is very old. However, with the advent of mass media in the second half of the 20th century, it gained enormous significance.
Parasympathetic nervous system
The parasympathetic nervous system is part of the vegetative or autonomic nervous system. The latter term refers to the fact that this part of the nervous system is not subject to voluntary control. It controls the activities of most of the internal organs as well as the heartbeat. In contrast to its counterpart, the sympathetic nervous system, the parasympathetic nervous system is most active when the body is at rest. Among other things, it controls digestion and urination. Acetylcholine serves as the messenger substance for signal transmission within the parasympathetic nervous system.
Parietal lobe
The parietal lobe is one of the four large lobes of the cerebral cortex. It is located behind the frontal lobe and above the occipital lobe. Somatosensory processes take place in its anterior region, while sensory information is integrated in its posterior region, enabling the handling of objects and spatial orientation. In addition, the parietal lobe is involved in attention, the recognition of body parts and objects, as well as linguistic and mathematical abilities.
Parvocellular
"Parvus" means "small." In the lateral geniculate nucleus, the switching station for visual stimuli in the thalamus, the outer four layers are called parvocellular because, unlike the magnocellular cell layers, they have small cell bodies. The parvocellular system transmits information for the perception of color and fine details.
Periaqueductal gray
A core area in the brain stem that is involved in defensive behavior and fear and flight reflexes via close connections to the limbic system. It also plays an important role in pain suppression by regulating signals from the spinal cord to the brain. It is considered an endogenous pain control system and is an important target for medication.
Perceptual field
The totality of all impressions that reach an individual at a given moment. This includes both stimuli from the environment and internal states that a living being perceives either consciously or unconsciously and combines into an overall picture.
Phantom limb
A phantom limb is still felt by the patient even though it has been amputated. The sensations are usually tingling or negative in nature, often in the form of pain.
Phantom limb pain
Phantom pains are called phantom pains because they occur in phantom limbs – limbs that have been amputated.
Plaques
Senile plaques accumulate in the gray matter of the brain when a protein – known as amyloid precursor protein – is not broken down correctly. Inflammation and disorders of fat or sugar metabolism can promote plaque formation. On average, the deposits reach a diameter of 50 micrometers. The appearance of plaques is one of several anatomical changes in the brain that pathologists can use to diagnose Alzheimer's disease after death.
Plasticity
The term neuroplasticity describes the ability of synapses, nerve cells, and entire areas of the brain to change structurally and functionally depending on the degree to which they are used. Synaptic plasticity refers to the adaptation of the signal transmission strength of synapses to the frequency and intensity of incoming stimuli, for example in the form of long-term potentiation or depression. In addition, the size, interconnection, and activity patterns of different areas of the brain also change depending on their use. This phenomenon is referred to as cortical plasticity when it specifically affects the cortex.
Pons
Area in the brain stem between the medulla oblongata and the mesencephalon. It acts as a switching station for many nerve pathways between the brain and spinal cord and contains numerous nuclei, including cranial nerves and those involved in controlling motor function in cooperation with the cerebellum.
Positron emission tomography
An imaging technique that helps doctors visualize metabolic processes in the body. The patient is injected with a weakly radioactive substance that emits positrons, i.e., beta radiation. When the positrons encounter electrons in the body, energy is released in the form of two photons. These photons travel in opposite directions. Detectors are arranged around the patient in the PET scanner to register the photons that strike them. This makes it possible to track whether the radioactive substance accumulates in certain areas of the body, which can indicate the presence of a tumor, for example. Positron emission tomography is also used in the early diagnosis of dementia. The radiation exposure is low and acceptable in a medical context.
posterior
A positional term – posterior means "towards the back, located at the rear." In relation to the nervous system, it refers to a direction towards the tail.
Posterior parietal cortex
The posterior parietal lobe receives inputs from numerous visual, auditory, somatosensory, and proprioceptive cortical areas. It integrates this information into an overall spatial picture that enables orientation, spatial attention, and the planning and execution of goal-directed movements.
Postcentral gyrus
The postcentral gyrus is the fold on the surface of the cerebrum located immediately behind the central sulcus. It contains the primary somatosensory cortex, where touch, pressure, temperature, and proprioceptive stimuli are processed.
Pre-dementia
Alzheimer's disease typically progresses through several clinical stages, preceded by an early phase with initial cognitive impairments. This phase, formerly known as pre-dementia, is now usually referred to as mild cognitive impairment (MCI) due to Alzheimer's disease. It can manifest itself through symptoms such as declining short-term memory. With modern imaging techniques, especially amyloid PET, characteristic amyloid deposits in the brain can already be detected in this early phase. Laboratory chemical analyses of blood or cerebrospinal fluid can also provide indications of changes in protein concentrations typical of Alzheimer's disease. Although the clinical diagnosis of dementia is only made in later stages, the underlying Alzheimer's pathology can often be detected in advance today.
prefrontal cortex
The prefrontal cortex (PFC) forms the front part of the frontal lobe and is one of the brain's most important integration and control centers. It receives highly processed information from many other areas of the cortex and is responsible for planning, controlling, and flexibly adapting one's own behavior. Its central tasks include executive functions, working memory, emotion regulation, and decision-making. In addition, the PFC plays an important role in the cognitive evaluation and modulation of pain.
Premotor cortex
Part of the motor cortex in the frontal lobe. It is connected to the primary motor cortex and numerous other brain regions and is involved in the planning, preparation, and coordination of complex, voluntary movements. Examples of its functions include reaching for an object or the sequence of movements involved in targeted actions.
Primary auditory cortex
The first processing station in the cerebral cortex for auditory information. The primary auditory cortex is located in the Heschl's gyrus and receives inputs from the medial geniculate nucleus of the thalamus. It is organized tonotopically – its neurons are arranged continuously according to frequency.
Primary gustatory cortex
Term for the areas of the insular cortex where information from the taste receptors is processed. Further processing takes place in the secondary gustatory cortex in the orbitofrontal cortex.
Primary motor cortex
An area of the frontal lobe in the anterior wall of the central sulcus. It is considered to be the higher-level control unit responsible for voluntary and fine motor skills. This is where the cell bodies of the central motor neurons are located, whose axons primarily extend to the spinal cord (via the corticospinal tract). Only in the primary motor cortex do Betz giant cells occur, which are particularly large motor neurons whose axons extend directly to the motor neurons in the anterior horn of the spinal cord without prior synaptic switching.
Primary somatosensory cortex
Area of the cerebrum where haptic stimuli are processed centrally. Anatomically, the somatosensory cortex is located on the first cerebral gyri behind the central sulcus. This is where afferents from sensory cells throughout the body converge. Neurons that evaluate information from neighboring areas of the body are also located next to each other in the somatosensory cortex. Neuroscientists refer to this as somatotopy.S1 is an important station in pain processing – this is where we become aware of the pain stimulus.
Primary visual cortex
The part of the occipital lobe whose primary inputs originate from the visual system. According to Brodmann, who originally divided the cerebral cortex into 52 areas in 1909, the primary visual cortex is area 17.
Priming
Priming refers to the influence of previous experiences on perception, reactions, or memory content. This often involves presenting a stimulus (e.g., a word, image, or symbol), often unconsciously or below the threshold of perception. Although the person is not consciously aware of this stimulus, it affects the processing of subsequent stimuli: for example, reactions become faster or memory content is retrieved more easily.
Projection neuron
A neuron that transmits information via its axon (long fiber-like extension of nerve cells) from one area to another, distant area, projects.
Propranolol
A medication for high blood pressure – a beta blocker. Beta blockers prevent the effects of adrenaline and noradrenaline.
Proprioception
Proprioception is the sense of oneself, or more precisely, the position of one's own limbs and the location of the body in space. It is made possible by certain receptors in muscles, joints, and tendons that constantly send information to the brain. Visual signals and those from the vestibular system are also processed. This enables coordination, balance, and targeted movements without constant visual control.
Procedural memory
Procedural memory is a form of non-declarative long-term memory. It includes sequences of actions such as riding a bike, playing the piano, or drawing a specific figure.
Psychosomatics
Psychosomatics examines the effects of emotional and cognitive processes on the body, particularly on the subjective perception of illness. This includes mental health problems with physical consequences, such as eating disorders and hypochondria. After psychologists initially used theoretical models to explain psychosomatic phenomena, the field has also been the subject of scientific research since the mid-20th century. Since 2003, there have been officially recognized specialists in psychosomatic medicine and psychotherapy.
Pulvinar
The pulvinar is a fairly large nucleus in the posterior thalamus that is connected to many visual centers. It appears to increase the excitability of cells in the visual cortex as soon as a stimulus is noticed. Some studies suggest that the pulvinar may also indirectly support language processing via cortical connections.
Pupil
The opening in the eye through which light enters. The size of the pupil is determined by the iris and changes reflexively (pupillary reflex). This process of adjusting to the brightness of the environment is called adaptation.
Purkinje cell
Purkinje cells are the main output cells of the cerebellar cortex and central switching points of the cerebellum. They have a dense, tree-like dendritic apparatus through which they receive information from thousands of parallel fibers and climbing fibers. Their axons are the only ones that extend out of the cerebellar cortex and project onto the nuclei of the cerebellum, from where signals are transmitted to motor centers. Purkinje cells are among the largest cell types in the cerebellum.
Putamen
A nucleus of the basal ganglia that, together with the caudate nucleus, forms the striatum. As part of the extrapyramidal motor system, it is involved in voluntary motor function (intentional movement).
Pyramidal pathway
The pyramidal pathway is a system of axons (long fiber-like extensions of nerve cells) that run from the motor cortex to the spinal cord. 80 percent of all fibers cross to the opposite side in the medulla oblongata. In the medulla, it runs past the pyramids, from which it gets its name. It is involved in fine and voluntary motor skills.
Pyramidal neurons
Pyramidal neurons are the most common neurons in the cerebral cortex. They are particularly large, and their "three-pointed" cell body resembles a cone or pyramid when viewed in cross-section.
Pain memory
Acute pain can become chronic if it persists for a long time or if the nervous system becomes permanently sensitized. Due to its plasticity, the nervous system can then react to even slight stimuli with pain, even if these would normally be harmless.
Pacinian corpuscle
Relatively large mechanoreceptors in the subcutaneous tissue that respond to vibration and thus also register acceleration on the skin.
They are named after the German anatomist Abraham Vater (1684–1751) and the Italian anatomist Filippo Pacini (1812–1883).
Perception
The term describes the complex process of gathering and processing information from stimuli in the environment and from the internal states of a living being. The brain combines the information, which is perceived partly consciously and partly unconsciously, into a subjectively meaningful overall impression. If the data it receives from the sensory organs is insufficient for this, it supplements it with empirical values. This can lead to misinterpretations and explains why we succumb to optical illusions or fall for magic tricks.
Reticular formation
The reticular formation is a network of numerous nuclei in the brain stem. It has a variety of tasks, for example, it is responsible for alertness, the integration of motor, sensory, and vegetative processes, and the sleep-wake cycle.
Retina
The retina is the inner layer of the eye covered with pigment epithelium. The retina is characterized by an inverse (reversed) arrangement: light must first pass through several layers before it hits the photoreceptors (cones and rods). The signals from the photoreceptors are transmitted via the optic nerve to the processing areas of the brain. The reason for the inverse arrangement is the evolutionary development of the retina, which is a protrusion of the brain.
The retina is approximately 0.2 to 0.5 mm thick.
Raphe nuclei
The raphe nuclei are located in the reticular system and are distributed throughout the brain stem. They belong to the ascending reticular activating system (ARAS) and are the site of serotonin production.
Red nucleus
The "red nucleus" owes its name to its high iron content. It can be seen with the naked eye as a large, round, reddish-colored nucleus in the midbrain. It belongs to the extrapyramidal motor system, and its central tasks are posture and muscle tone.
Reissner membrane
This membrane separates the scala media from the scala vestibuli in the cochlea.
Releasing hormone
Hormones of the hypothalamus that promote the release of other hormones in the adenohypophysis.
REM sleep
"REM" stands for "rapid eye movement" – and rapid eye movements are also characteristic of REM sleep. During the course of a night, we go through several such REM phases, which are interrupted by non-REM phases. REM sleep is characterized by rapid eye movements, low-amplitude brain activity of mixed frequencies, and reduced muscle tone. Pulse and respiratory rate, on the other hand, are increased. In addition, we dream particularly vividly and intensely during these phases. People who are awakened from REM sleep often report vivid, concrete, and emotional dreams, while those awakened from non-REM sleep tend to report more abstract dreams that resemble thoughts.
Retinal
A chemical synthesized from vitamin A. Together with opsin, it forms rhodopsin.
Retrograde amnesia
A form of memory disorder in which memories from before the damage occurred can no longer be retrieved. The affected period can vary greatly and range from just hours before the event to entire decades.
Receptive field
The receptive field is the area of the environment in which a stimulus changes (increases or decreases) the activity of a specific nerve cell.
Receptor
A receptor is a protein, usually located in the cell membrane or inside the cell, that recognizes a specific external signal (e.g., a neurotransmitter, hormone, or other ligand) and causes the cell to trigger a defined response. Depending on the type of receptor, this response can be excitatory, inhibitory, or modulatory.
Rhodopsin
A specific opsin found in the rods of the retina.
rostral
A positional term – rostral means "towards the beak." In relation to the nervous system, it refers to a direction along the neural axis towards the front, towards the face.
In animals (without upright gait), the designation is simpler, as it always means located toward the front. Due to the upright gait of humans, the brain bends in relation to the spinal cord, making rostral at the level of the back become "up."
Resting potential
The membrane potential of a neuron at rest. The inflow and outflow of ions are in equilibrium. It ranges from –50 to –100 mV.
Round window
The round window is a membrane-covered opening in the cochlea on the middle ear side. It is connected to the scala tympani and enables the necessary pressure equalization in the inner ear when sound is transmitted through the oval window.
Rods
The rods are light-sensitive cells with high light sensitivity. They react even to weak light and are therefore responsible for scotopic vision, black-and-white vision, and vision at dusk. The rods are concentrated in the outer areas of the retina and therefore do not provide high visual acuity.
Stress disorder
In psychology, stress disorder refers to the pathological reaction to prolonged or short-term extreme stress, such as trauma. A distinction is made between acute stress disorder, also known as a nervous breakdown, and post-traumatic stress disorder. In both cases, the symptoms are the same, although in acute stress disorder they do not last longer than four weeks.
Semicircular canals
The three semicircular canals per ear are interconnected, fluid-filled tubes that are positioned almost at right angles to each other and belong to the balance organ in the inner ear (vestibular apparatus). They serve to register angular accelerations, i.e., rotational movements of the head.
Superior colliculus
The upper pair of hills of the four hills of the midbrain (tectum) are also referred to in the plural as colliculi superiores. They form a switching center in the optical system for reflex movements of the eyes and for pupil reflexes.
Simple cell
An orientation-sensitive cell in the primary visual cortex (part of the cerebral cortex) whose receptive field is divided into ON and OFF subfields. For example, it reacts strongly to lines of a certain orientation.
Savant syndrome
Savant syndrome is a rare phenomenon in which people with cognitive deficits in one or more very limited areas possess astonishing abilities – for example, reciting six-digit prime numbers or drawing a city correctly from memory in detail after flying over it. Probably the best-known savant was Kim Peek, the inspiration for the film Rain Man.
Short-term memory
Short-term memory is a type of temporary storage in the brain where information can be retained for a few seconds to a few minutes. Its capacity is very limited, at 7±2 units of information (chunks). These can be numbers, letters, or words, for example. Today, this memory is usually considered within the framework of the working memory model, which also emphasizes the active processing of content.
Sodium-potassium pump
The sodium-potassium pump is a protein in the cell membrane. When energy is consumed, it transports three sodium ions from inside the cell to the external environment and, in return, two potassium ions from the external environment to inside the cell.
Subthalamic nucleus
Although the subthalamic nucleus is a nucleus of the subthalamus in the diencephalon, it is functionally closely involved in the motor control of the basal ganglia. Damage to this nucleus can lead to temporary, uncontrolled, jerky movements of the extremities – known as ballism.
Suprachiasmatic nucleus
A nucleus of the hypothalamus that plays a central role in circadian rhythms, including the sleep-wake cycle. It is the master clock, the body's most important internal clock, controlling melatonin production in the epiphysis. It receives direct input from the retinal ganglion cells.
Supraoptic nucleus
A core area of the hypothalamus, located above the optic nerves. This is where the peptide hormones vasopressin and oxytocin are produced.
Spinal paralysis
This is the term used by doctors to describe a combination of symptoms that occur when the nerve cord in the spinal cord is severed. The location of the injury on the spine is decisive for its consequences: the body can no longer control limbs and organs whose innervation branches off from the spinal cord below the damaged area. Possible consequences range from partial paralysis of the limbs to complete loss of control over the rectum and bladder. Also called paraplegia or paraparesis.
Spinal cord
The spinal cord is the part of the central nervous system located in the spine. It contains both the white matter of the nerve fibers and the gray matter of the cell nuclei. Simple reflexes such as the knee-jerk reflex are already processed here, as sensory and motor neurons are directly connected. The spinal cord is divided into the cervical, thoracic, lumbar, and sacral spinal cord.
Saccade
Rapid eye movement, which usually occurs unconsciously. It is a quick and jerky movement of the eyes, in which the eye spontaneously focuses on an object. When reading, for example, the eyes jump from one short word to the next. During a saccade, visual information processing is greatly reduced.
Saltatory conduction
The term is derived from the Latin "saltare" – to jump. And this is exactly what an impulse does along a myelinated nerve: it jumps from one Ranvier node to the next, which greatly increases the speed of nerve conduction.
Sleep phases
During sleep, we go through several non-REM/REM cycles, each lasting around 90 minutes. The non-REM phases consist of stages N1, N2, and N3, with slow delta waves with frequencies of 0.5–2 Hz dominating in N3 (deep sleep). REM sleep is characterized by rapid eye movements, low-amplitude, mixed-frequency brain activity, and greatly reduced muscle tone. Deep sleep predominates at the beginning of the night, while the proportion of REM sleep increases in later cycles.
Sleep disorders
A collective term for various phenomena characterized by the fact that those affected do not get restful sleep. Both psychological and organic causes can contribute to this. Symptoms range from problems falling asleep and staying asleep to undesirable behaviors during sleep such as sleepwalking, restless legs when falling asleep, sleep apnea, etc. According to estimates, up to 30 percent of all adults in Western countries suffer from some form of sleep disorder. Finding the causes is often complicated, and analysis in a sleep laboratory is the best method of investigation.
stroke
In a stroke, the brain or parts of it are no longer supplied with sufficient blood, which impairs the supply of oxygen and glucose. The most common cause is a blockage in an artery (ischemic stroke), less commonly a hemorrhage (hemorrhagic stroke). Typical symptoms include sudden visual disturbances, dizziness, paralysis, speech or sensory disturbances. Long-term consequences can include various sensory, motor, and cognitive impairments.
Secretases
Secretases are proteases that cleave proteins into smaller fragments, often membrane-bound in the case of transmembrane proteins. Cleavage produces intracellular fragments that can act as signals and extracellular fragments that are released into the environment. Some proteins, such as the amyloid precursor protein (APP), offer different cleavage sites for different secretases. Beta-amyloid, the main component of senile plaques, is formed when APP is first cleaved by β-secretase outside the membrane and then by γ-secretase inside the membrane.
Secondary auditory cortex
The secondary auditory cortex is an area in the temporal lobe (temporal lobe) that is downstream of the primary auditory cortex. It processes complex auditory information such as speech, sounds, and music, and plays a role in recognizing patterns in acoustic signals. Wernicke's area, which specializes in language comprehension, is located within this area but is not synonymous with the entire secondary auditory cortex.
Second messenger
A second messenger is a chemical substance that transmits a signal within the cell after a receptor on the cell membrane has been activated. It is formed or released intracellularly and mediates the effect of the original signal on various target structures in the cell, often amplifying the signal.
Secondary somatosensory cortex
The posterior parietal lobe receives input from numerous other cortex areas - this is where visual, auditory and proprioceptive signals are integrated into a whole, enabling orientation and movement in space. The S2 cortex, located posterior and ventral to S1, is also involved in the conscious processing of pain.
Self-fulfilling prophecy
Term for the phenomenon whereby certain expectations influence behavior in such a way that these expectations are fulfilled. For example, if a teacher considers individual students to be particularly high achievers, this attitude on the part of the authority figure can lead to the students in question developing a high level of self-confidence and, as a result, actually performing exceptionally well.
Self-fulfilling prophecy
Term for the phenomenon whereby people change their behavior based on certain expectations regarding a future event in such a way that the event does not occur. For example, a warning of a bomb attack may prompt the hiring of additional security personnel, who ultimately prevent the attack.
semantic memory
Semantic memory is a form of declarative long-term memory. It stores knowledge about the world, i.e., facts, formulas, geography, recipes, etc.
Sensitization
If a stimulus – a touch, a sound – proves to be important on multiple occasions, the nervous system will respond more intensely to this stimulus in the future. This sensitization is a learning process that also takes place at the cellular level. The opposite is habituation.
Sensory transduction
In the process of transduction, a sensory stimulus – such as light or touch – is converted into a nerve impulse.
Sensory neuron
A sensory neuron is a specialized nerve cell that perceives stimuli – for example, chemical (sweet), visual (bright), or acoustic (loud) – and transmits the information to the central nervous system.
Septum
The septal nuclei are located medially in the basal forebrain, near the anterior tip of the cingulate gyrus. They are connected to the olfactory cortex and linked to other limbic structures via the fornix. Functionally, they play a role in emotional processes and reward processing.
Serotonin
A neurotransmitter that acts as a messenger in the transmission of information between neurons at their synapses. It is primarily produced in the raphe nuclei of the brain stem and plays a key role in sleep and alertness, as well as emotional well-being.
SNP
SNPs (single nucleotide polymorphisms) are locations in the genome where the DNA sequence differs between individuals of the same species. Researchers have identified around 200 million SNPs in the human genome. They occur both in coding DNA regions, which are responsible for proteins, and in regulatory or as not yet understood sections. SNPs provide valuable information about the development of populations and are particularly interesting in medicine when they are associated with certain diseases.
Soma
The cell body, also known as the soma, is the metabolic center of the cell. In addition to the cell organelles – such as the mitochondria – it also contains the cell nucleus with the genetic material. The dendrites and axon (long, fiber-like extension of nerve cells) extend from the cell body.
Somatosensory system
Somatosensory perception is the body's sensory perception: temperature, pressure, and pain are typical sensations of the skin. However, somatosensory perception also includes depth perception, i.e., position in space, movement, and the position of muscles and joints.
Spinal nerves
Spinal nerves are the nerves that emerge from the spinal cord. The cell bodies of their neurons are located in the gray matter of the spinal cord.
Spinocerebellum
The area of the cerebellum that includes the cerebellar vermis and its adjacent areas. Involved in muscle tone and walking movements.
Stirrup
The stapes is the third ossicle in the middle ear and the smallest bone in the human body. It transmits its vibrations to the oval window, behind which the inner ear begins.
Stigma
The term refers to a characteristic that is viewed negatively by society or a group and leads to the discrediting of individuals who possess this characteristic. Stigmas can refer, for example, to members of certain ethnic groups or marginalized social groups. Even a diagnosis of a mental disorder or an illness such as AIDS can be accompanied by stigmatization, depending on the social environment.
Stress hormone system
During the stress response, the sympathetic nervous system and a number of hormone glands – the hypothalamus, pituitary gland, and adrenal cortex – work together to prepare the body for increased demands. The sympathetic nervous system uses the hormones adrenaline and noradrenaline as messenger substances. Their activity increases breathing and heart rate while improving blood flow to the muscles. During the stress response, the adrenal cortex releases the hormone cortisol. It acts via negative feedback on the hypothalamus and pituitary gland, thereby slowing down further cortisol release. When the stressor subsides and the sympathetic tone decreases, the parasympathetic nervous system can regain the upper hand and bring the organism into a state of rest.
Striatum
The striatum is a central structure of the basal ganglia. It consists of the caudate nucleus and putamen; the nucleus accumbens is also functionally part of it as its ventral portion. As the most important input structure of the basal ganglia, the striatum plays an essential role in controlling movement sequences as well as in cognition, motivational processes, and the reward system.
Subiculum
The transition zone between the cornu ammonis and the entorhinal cortex is called the subiculum.
Substantia nigra
A nucleus complex in the ventral mesencephalon that plays a central role in initiating and modulating movement. It appears dark due to neuromelanin. Its dopaminergic neurons project via the nigrostriatal pathways to the putamen and caudate nucleus. Failure of these neurons leads to the typical symptoms of Parkinson's disease.
Substance P
Substance P is a neuropeptide that acts as a neurotransmitter and belongs to the tachykinin family. High concentrations are found in the dorsal horn of the spinal cord, where it is involved in pain modulation.
Subthalamic nucleus
Although the subthalamic nucleus is a nucleus of the subthalamus in the diencephalon, it is functionally closely integrated into the motor control of the basal ganglia. It plays a role in impulse control, movement control, and inhibition of unwanted movements. Damage to this nucleus can lead to temporary, uncontrolled, jerky movements of the extremities – known as ballism. Doctors have already achieved successful treatment outcomes in both obsessive-compulsive disorder and Parkinson's disease by artificially stimulating this region with a neuroimplant.
Subthalamus
The subthalamus is an area of the diencephalon located ventrally below the thalamus. It includes the subthalamic nucleus, which functionally belongs to the basal ganglia network. The subthalamus plays an important role in the regulation and inhibition of movement sequences and in impulse control.
Superior temporal sulcus
The superior temporal sulcus is the uppermost groove of the temporal lobe and lies below the Sylvian fissure. It separates the superior temporal gyrus from the middle temporal gyrus. Functionally, this area is involved in auditory processes, language processing, and the perception of socially relevant information.
Supplementary motor area
Area of the association motor cortex in the frontal lobe that is involved in movement planning and the organization of movement sequences.
Sympathetic nervous system
Part of the autonomic nervous system, whereby the sympathetic nervous system primarily transmits excitatory impulses – in contrast to its counterpart, the parasympathetic nervous system. For example, the sympathetic nervous system activates respiration, the heart, and circulation, but it also affects the smooth muscles of all internal organs. The sympathetic nervous system uses the neurotransmitters acetylcholine and norepinephrine.
Synapse
A synapse is a connection between two neurons and serves as a means of communication between them. It consists of a presynaptic region – the terminal button of the sender neuron – and a postsynaptic region – the region of the receiver neuron with its receptors. Between them lies the synaptic cleft.
Synaptic depression
Weakening of signal transmission at a synapse due to reduced neurotransmitter release or decreased receptor sensitivity; occurs, for example, with repeated stimulation (habituation).
Synesthesia
Synesthesia is the linking of two or more sensory perceptions to form a subjective sensation. For example, a synesthete might always associate the number seven with the color red. Synesthesia appears to have a hereditary component, but it can also be caused by illness (e.g., schizophrenia) or drugs (e.g., hallucinogens).
Sensory memory
This memory allows sensory input – a sentence or an image – to be repeated without having been consciously perceived. Each sensory modality has its own memory for this purpose, which is deleted after a very short time. The ability to repeat something that was said earlier in a conversation, even though you were not paying attention to it, is an example of auditory sensory memory.
Theory of emotions
Emotions still pose many questions for researchers today: Are there primary and secondary emotions? Are there universal emotions? Are there connections between individual emotions? Different theories of emotion seek answers to questions like these.
Terminal button
The end of an axon (long, fiber-like extension) of a nerve cell is called a terminal bouton if it is the presynaptic part of a synapse. The terminal bouton is a spherical thickening containing vesicles (small sacs) that store neurotransmitters (chemical messengers in the brain).
Threshold potential
In order for an action potential to be triggered, the membrane potential at the axon hillock of a neuron must exceed the threshold value of approximately –50 mV (relative to the resting potential of –70 mV). This is the threshold potential. If the depolarization remains below this threshold, no action potential is triggered.
Taste
The sensory impression we refer to as "taste" results from the interaction between our senses of smell and taste. In terms of sensory physiology, however, "taste" is limited to the impression conveyed to us by the taste receptors on the tongue and in the surrounding mucous membranes. It is currently assumed that there are five different types of taste receptors that specialize in the taste qualities sweet, sour, salty, bitter, and umami. In 2005, scientists also identified possible taste receptors for fat, whose role as a distinct taste quality is still being investigated.
Taste bud
Taste buds are groups of taste cells in the oral mucosa and are therefore the site of taste perception.
Taste papilla
Taste papilla are specific surface structures on the tongue that contain taste receptors. They are distinguished by their size, shape, and density of taste receptors. There are wall, leaf, mushroom, filament, and lentil papillae.
Tympanic duct
The tympanic duct or scala tympani is the lower of the three canals of the cochlea. Like the scala vestibuli, this canal is also filled with a lymph-like fluid.
Tau protein
Tau proteins are particularly prevalent in the central nervous system. Their function is to stabilize microtubules – the structures that give cells their shape and support. Under certain circumstances, enzymes attach too many phosphate groups to tau proteins. As a result, the proteins are no longer broken down properly and form toxic aggregates within the neurons. Alongside senile plaques, aggregated tau proteins are considered a classic hallmark of Alzheimer's disease.
Tegmentum
Tegmentum (from the Latin "tegere," meaning "to cover"). This is the ventral part of the midbrain located beneath the aqueduct. It contains nuclei such as the substantia nigra, the reticular formation, the cranial nerve nuclei, and the red nucleus.
Tectorial membrane
The tectorial membrane is a gelatinous layer into which the cilia of the outer hair cells protrude. The shear movements caused by sound between the basilar membrane and the tectorial membrane are registered by the cilia.
Temporal lobe
The temporal lobe is one of the four lobes of the cerebrum and is located laterally (on the side) at the bottom. It contains important areas such as the auditory cortex and parts of Wernicke's area, as well as areas for higher visual processing; deep within it lies the medial temporal lobe with structures such as the hippocampus.
Temporo-parietal junction
The transition between the temporal and parietal lobes – i.e., the temporal and parietal lobes – of the cerebral cortex. Here, in the posterior region of the Sylvian fissure, information from the limbic system, the thalamus, and the visual, auditory, and somatosensory cortex is integrated. Accordingly, the temporo-parietal junction forms an anatomical and functional hub of the brain that helps us develop complex abilities, including the ability to recognize biological movement or the ability to empathize with other people.
Thermoreceptor
Free nerve endings that serve as receptors for temperature sensations in the skin.
Trajectory
A physical term that describes the trajectory, or path, of an object – for example, a thrown object.
Transducin
A G protein found in the photoreceptors of the retina. It is activated when a photon hits a photopigment and causes the cation channels in the photoreceptor to close. It is therefore an important component of the visual signal transduction cascade.
Transcranial direct current stimulation
A therapeutic procedure in which a weak electrical current is conducted from the outside into the brain with the aid of electrodes. This is intended to stimulate the formation of new connections there. Transcranial direct current stimulation was originally developed for the treatment of brain trauma. Today, neurologists also use it to relieve migraine attacks and headaches. However, the effectiveness of the procedure is controversial.
Trigeminal nerve
In accordance with its literal translation, "triple nerve," the trigeminal nerve consists of three main branches: the ophthalmic branch, the maxillary branch, and the mandibular branch. The trigeminal nerve originates in the brain, where it is connected to four different nerve nuclei – three sensory and one motor. It reaches large parts of the head via the three branches. The sensory and motor fibers supply the face, nasal and oral cavities, and masticatory muscles.
Tuber cinereum
The tuber cinereum is a hill-shaped area in the hypothalamus from which the infundibulum, the pituitary stalk, originates. The tuber nuclei are located in the tuber cinereum, including the nucleus tuberomammillaris, which is the only region in the brain that uses histamine as a neurotransmitter.
Tectum
A structure in the midbrain consisting of two pairs of mounds, the upper colliculi and the lower colliculi.
Twin studies
Pairs of twins are valuable subjects for human geneticists and psychologists who want to find out to what extent certain characteristics are genetically determined and what role environmental conditions play. Of particular interest here is how much more similar identical twins are compared to fraternal twins.
The degree of genetic similarity differs between identical (100%) and fraternal twins (50%). However, they live in a similar environment, so the degree of greater similarity between identical twins compared to fraternal twins can be used to estimate the genetic contribution to traits such as intelligence. In this case, depending on the study, it was estimated to be between 50 and 80 percent, depending on whether the environmental differences in the population (health care, access to education) are large or small.
Vitreous body
The vitreous body consists of a gel-like substance inside the eye that supports the shape of the eye.
Ventrolateral nuclei
The lower lateral nucleus group of the thalamus is responsible for motor function (movement). It receives inputs from the cerebellum and basal ganglia and has outputs to motor and premotor areas of the cerebral cortex.
Vestibular duct
The vestibular duct or scala vestibuli is the uppermost of the three canals of the cochlea and is filled with perilymph. At the oval window, the movements of the stapes transmit vibrations to the perilymph of the scala vestibuli. These vibrations set the basilar membrane in motion and thus indirectly influence the middle canal, the scala media.
Visual pathway
The visual pathway refers to the network of nerve cells involved in visual perception. In mammals, it runs from the retinal ganglion cells in the eye – as the optic nerve to the optic chiasm, then as the visual tract – via the only switching point in the lateral geniculate nucleus to the primary visual cortex.
Visual radiation
The optic radiation – also known as Gratiolet's optic radiation after its discoverer – distributes visual impulses from the lateral geniculate nucleus to the comparatively very large primary visual cortex.
vascular
The term refers to vessels in the body in which fluids such as blood or lymph circulate. In a narrower sense, doctors refer to the network of veins, arteries, and capillaries as the "vascular system." If the vascular system is blocked, for example as a result of a stroke, less blood reaches the brain. This means that it receives less oxygen and other nutrients. This can lead to impaired cognitive functions and the development of "vascular dementia." After degenerative forms of dementia such as Alzheimer's, vascular dementia is the second most common form of this group of diseases.
ventral
A positional term – ventral means "towards the abdomen." In relation to the nervous system, it refers to a direction perpendicular to the neural axis, i.e., downwards or forwards.
In animals (that do not walk upright), the term is simpler, as it always means toward the abdomen. Due to the upright posture of humans, the brain bends in relation to the spinal cord, making ventral mean "forward."
Ventral tegmental area
Located in the midbrain, the uppermost section of the brain stem, is the ventral tegmental area (VTA) – a central component of the reward system. The area itself is not particularly large, but its influence is immense: the neurons of the VTA send their axons to the nucleus accumbens and widely into the prefrontal cortex (PFC), where they release the neuromodulator dopamine. In this way, they enhance learning processes, but can also contribute to the development of addictions.
Ventricular system
A system of cavities in the brain filled with cerebrospinal fluid (CSF). This provides protection, nutrition, homeostasis, and waste removal for the brain.
Ventromedial prefrontal cortex
Anatomically, the ventromedial prefrontal cortex belongs to the frontal lobe of the cerebral cortex. In some patients with decision-making problems, neuroscientists find lesions in this region of the brain. The ventromedial prefrontal cortex also becomes active when we try to suppress negative emotions such as feelings of guilt. It receives signals from many other areas of the brain and innervates the amygdala, hypothalamus, and several areas of the cortex.
Vermis
The vermis is an unpaired structure of the cerebellum located on the midline. It primarily receives somatosensory inputs.
Vestibular system
The vestibular system is part of the inner ear. Its sensors are located in the semicircular canals. As part of the balance system, it detects circular movements (rotations), acceleration, and gravity.
Vestibulo-ocular reflex
When we turn our head, our eyes automatically move in the opposite direction. This reflex ensures that a stable image is formed on the retina even when the head moves quickly. This is made possible by the connection between the semicircular canals of the vestibular system and the nerve nuclei of the eye muscles in the brain stem.
Visual agnosia
Agnosia can be translated as "not recognizing." It refers to deficits in visual perception without blindness. The term was coined by Sigmund Freud. Examples of visual agnosia include prosopagnosia (face agnosia) and object agnosia.
Visual association cortices
The visual association cortices are the areas that are not involved in primary visual processing but play a major role in the interpretation and integration of visual information. They process, for example, shape, color, movement, or spatial orientation and forward information along the what pathway (ventral) for object recognition and the where/how pathway (dorsal) for spatial processing and action control.
\Viewpoint invariance
This term refers to a phenomenal ability of our brain: it is able to recognize the same object over and over again – no matter from which angle we view it and largely regardless of how much the object has changed in the meantime.
Visual cortex
The visual cortex refers to the areas of the occipital lobe that are involved in processing visual information. These include the primary visual cortex and the associative visual cortices V1 to V5. According to Brodmann, the visual cortex comprises areas 17, 18, and 19.
Visual system
The visual system is the part of the nervous system that processes visual information. It primarily comprises the eye, the optic nerve, the optic chiasm, the optic tract, the lateral geniculate nucleus, the optic radiation, the primary visual cortex, and the visual association cortices.
Volition
This psychological term describes the cognitive process in which an individual decides on an action and carries it out. In simple terms, volition can also be described as an act of will or the will to initiate action.
Ventral pathway
The part of the visual processing pathway that deals with size, shape, color, and ultimately object recognition. The what pathway runs from V1 and V2 to the areas of the temporal lobe.
working memory
A form of memory, often used synonymously with the term "short-term memory." However, many theorists clearly distinguish between the two concepts with regard to the manipulation of information in working memory. It temporarily retains information, including newly acquired information and memory content from long-term memory that is associated with the new information. In the model developed by Alan Baddeley and Graham Hitch, it includes a central executive, a phonological loop, an episodic buffer, and a visuospatial sketchpad.
white matter
The white matter refers to the myelinated fibers of the nervous system that connect one neuron to another. The white color is caused by the myelin sheath surrounding the fibers.
Williams-Beuren syndrome
Williams-Beuren syndrome is a rare developmental disorder that is genetically determined. Those affected are missing 26-28 genes on chromosome 7. One of these genes is crucial for the development of connective tissue, which is why it cannot form properly in people with Williams-Beuren syndrome. Other characteristics include prominent cheekbones, a bulbous nose, and usually mild to moderate cognitive impairment, while language skills and social interaction are often relatively well developed.
Zona incerta
Zona incerta – the name was coined by Auguste Forel and means that nothing certain can be said about this core of the diencephalon. That was in 1877, and since then it has been discovered that the zona incerta is very well connected throughout the brain. But its function remains unknown.
Zonules
The zonules are arranged in a radial pattern around the lens of the eye and connect it to the ciliary muscle.