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The claustrum is a relatively thin layer of gray matter located between the white matter tracts of the external capsule and extreme capsule of the basal ganglia. It is situated medial to the insular cortex and lateral to the putamen. This structure is best seen through the sagittal view, a perspective seen when the body is divided into left and right sections. It can range from one to two millimeters thick and several centimeters long. Although its function is not yet fully established, it is believed to play a role in emotions, arousal, and conscious integration, and it may play a role in dementia states.
Most neuroanatomists know where the claustrum brain part is located, but because of its thinness, it can be easily overlooked. It is said that its volume is only about 0.25% of the entire cerebral cortex. Its name is derived from the Latin word claustralis, which means isolated or secluded. Indeed, it is relatively isolated from the gray matter of the cerebrum.
An interesting fact about this structure is that unlike other parts of the brain, its cell population is relatively homogenous. In the other parts of the brain, cells differentiate into various cell types, and perform various functions. There are only three main cell types in the claustrum. The type 1 cells are large, have spine-covered dendritic processes, and receive input from and give output to various brain regions. Type 2 and 3 cells, called interneurons, are limited to the claustrum, lack spines, and differ in terms of cell body size.
Relatively little is known about the real function of this structure. The claustrum may play an important role in modality integration. When a person perceives an object, it has various characteristics, including shape, color, weight, sound, speed, and smell. These modalities have to be integrated to avoid confusion, and it seems that the claustrum plays a crucial role in this process. It is also believed that this structure plays a role in functional timing, which means that it helps in the simultaneous processing of information.
It has been discovered that people with dementia often have abnormalities in their claustrum. For instance, when brain specimens of people who were diagnosed with dementia with Lewy bodies or with Parkinson’s disease are examined, the claustrum often has alpha-synuclein neuron inclusions. These inclusions can further be classified as beta amyloid, Lewy bodies, and Lewy neurites. The presence of these inclusions is strongly associated with the dementia process.