The Cingulate Gyrus

The cingulate gyrus can only be seen when the brain is cut lengthwise down the middle and opened upIt is the part of the cerebral cortex above the corpus callosum that connects the two hemispheres. As the largest part of the limbic system, the cingulate gyrus influences attention, pain processing, and the regulation of emotions. It is also part of the Papez circuit, which begins and ends at the hippocampus and plays a key role in the permanent storage of memory content.

Gyrus cinguli is Latin for “belt fold.” Like a belt, it lies on the corpus callosum and runs parallel to it from front to back. However, it includes not only the cerebral cortex directly above the corpus callosum, but also its continuation into the sulcus that borders it above – the sulcus cinguli. Interestingly, the surface of the cingulate gyrus varies greatly from person to person: its sulci are located in different places, and in some people, the cingulate gyrus is even divided into two parallel gyri by an additional paracingular sulcus.

Together with the hippocampal gyrus, the cingulate gyrus forms the outer ring of the limbic system. The corpus callosum is the boundary between outer and inner ring, but the two are not really separated; the cingulate gyrus is well connected to all other parts of the limbic system via fiber connections.
 

Although it is not visible externally, internally, at the cellular level, the cingulate gyrus is divided into two parts with different functions. Their names are rather unimaginative: they are simply called Pars anterior and Pars posterior – the front part and the rear part.

The posterior cingulate gyrus is connected to different areas of the cerebral cortex in the parietal, temporal, and frontal lobes. It primarily regulates visual-spatial attention and is responsible for spatial memory. This may be due to the fact that it receives input from the posterior parietal lobe, which plays a key role in orientation. Cytologically, the posterior cingulate gyrus mainly contains nerve cells that are involved in sensory processing. Under the microscope, the many small cells in the granular layers of the cortex are striking.

The front part has been much better studied experimentally than the rear part. It exchanges information with the amygdala, the nucleus accumbens, the thalamus, the motor and prefrontal cortex, and is mainly composed of motor nerve cells. Its cortex is agranular, meaning that the granular cell layers typical of other brain areas are greatly reduced. The front part of the cingulate gyrus also plays a role in motor function: if it is damaged, those affected suffer from a lack of movement.

The anterior cingulate gyrus is active when it comes to choosing between different behaviors in response to conflicting stimuli. An example is the Stroop test: Test subjects must name the color in which a word is written. This is more difficult than one would suspect: between two conflicting stimuli – the word “red” written in green – attention must be directed to the correct answer. In addition, the anterior cingulate gyrus is involved in expressive movements, i.e., facial expressions and gestures. And last but not least, it is involved in the evaluation of pain stimuli. Professionals divide the anterior cingulate gyrus further into a posterior cognitive and an anterior affective subunit.
 

If the cingulate gyrus is stimulated with an electrode – i.e., activated – bodily functions change: An animal stimulated in this way breathes more slowly, its heart beats more slowly, its blood pressure drops, and its pupils dilate.

If, on the other hand, the cingulate gyrus is damaged – for example, by a stroke – the person affected reacts less to environmental stimuli and lacks drive: they move less and also speak less. If the lesion is more extensive and occurs on both sides of the brain at the same time, the person no longer even responds to pain stimuli – they turn toward the stimulus, so they do register it, but otherwise show no appropriate reaction. Monkeys that have had their cingulate gyrus removed become tamer, but at the same time lose all interest in other members of their group.

Neuroscientists suspect that the cingulate gyrus also plays a role in the development of neuropsychiatric disorders such as depression, obsessive-compulsive disorder, and schizophrenia. For example, people with schizophrenia lack drive and attention. They have noticeable problems with the Stroop test and make more mistakes. In addition, their cingulate gyrus is only slightly active when performing the tasks. Other studies have found that this part of the brain has reduced blood flow in schizophrenic patients and is smaller in volume than in healthy subjects. Postmortem examinations of brain tissue from schizophrenic patients revealed that certain nerve cells in the anterior part of the cingulate gyrus are smaller and less frequent in these patients.
 

First published on September 9, 2011
Updated on December 22, 2023