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- Glossary
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.
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- Glossary
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.
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- Glossary
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.
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- Glossary
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.
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- Glossary
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.
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- Glossary
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.
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- Glossary
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.
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- Glossary
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.
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- Glossary
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.
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- Glossary
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.
