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The claustrum is a thin, irregular, sheet of neurons that is attached to the underside of the neocortex in the center of the brain. It is suspected to be present in the brains of all mammals. The claustrum is a fraction of a millimetre to a few millimetres deep and is a vertical curved sheet of subcortical gray matter oriented sagittally between the white matter tracts of the external capsule and extreme capsule. The claustrum is lateral to the putamen and medial to the insular cortex and is considered by some sources to be part of the basal ganglia. There are lateral and medial tracts connecting the claustrum to many parts of the cortex and perhaps to the hippocampus, the amygdala, and the caudate nucleus (connections with subcortical centers are a matter of debate). One of the interesting features of the claustrum is the uniformity in the types of cells, indicating a uniform type of processing by all claustral neurons. Though organized into modality specific regions, the claustrum contains a great deal of longitudinal connections between its neurons that could serve to synchronize the entire anterior-posterior extent of the claustrum. Francis Crick and Christof Koch have compared the claustrum to the conductor of an orchestra, referring to its regulatory role in consciousness and cognition. The different parts of the cortex must play in harmony or else the result is a cacophony of sounds instead of a beautiful symphony. The claustrum may be involved in widespread coordination of the cerebral cortex, using synchronization to achieve a seamless timescale between both the two cortical hemispheres and between cortical regions within the same hemisphere, resulting in the seamless quality of conscious experience. ==Structure== The claustrum is a telencephalic subcortical structure. It is a thin sheet of grey matter underneath the inner part of the neocortex. It is on both sides of the brain, and can be found below the insular cortex, which deep to the temporal and parietal lobes at the deepest point of the lateral fissure, and above the outside of the putamen, which is a sub-structure of the basal ganglia. The sheet is approximately one to several millimeters thick, and can cover up to a couple centimeters length wise depending on the animal. One interesting aspect about the claustrum is the paucity of cell types. In most parts of the brain, especially in the cortical regions, there is considerable differentiation of cell types, giving way to a number of functions. In the claustrum, as Dr. Crick and others pointed out, there are three main types of cells. The first, which is deemed Type 1, is large with spine-covered dendritic processes. These cells receive input as well as project back toward various regions, both laterally and medially. The other two types of cells do not have spines, but can be told apart based on the cell body size. However, both are restricted to the claustrum and, thus, are labeled interneurons. It is clear that the claustrum projects to, and receives projections from, a number of cortices, including the primary motor, premotor, prefrontal, auditory, and visual, among others. In one study conducted in France by Judith Tanne-Gariepy et al. (9), these projections were traced back to segregated areas, including differentiated areas along the dorsoventral axis for the pre-supplementary motor area and supplementary motor area – proper. Projections from the claustrum to various sub-regions of the motor cortex were shown to overlap somewhat, but did show a degree of local segregation.〔〔 The truly interesting thing about the claustrum, however, is how it can take in multiple information modalities, including motor, visual, and auditory. It has even been shown that the same cells can process information across all these types, even though there is some semblance of segregation across a single type of information. There have also been a number of interesting studies looking at the proteins inside the claustrum. In one experiment performed at the University of South Carolina by J.R. Augustine et al.,〔Augistine JR. Calcium-binding proteins in the claustrum of the rhesus monkey. 2008. Society for Neuroscience. Program#/Poster#: 79.9/OO31〕 researchers looked at calcium-binding proteins in the rhesus monkey claustrum, including calbindin D28K, parvalbumin, and calretinin. After removing the brains and properly preserving them, the group used various antibodies and antiserums to detect the presence of the proteins. The calbindin proteins were shown as likely elements in the inhibitory circuitry of the claustrum, while the calretinin most likely served as calcium buffer to maintain homeostasis. Another study looked at the serotonergic innervation in the claustrum. The clear conclusion here was that, in the ventral claustrum where the visual projections are, the stained axons were short and arranged randomly. However, in the dorsal, non-visual section, of the claustrum, the fibers ran consistently in long lengths along the dorsal-ventral direction. Like many of the other studies, this is a good first step toward determining the true functions of the claustrum, although there is still much room for work. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Claustrum」の詳細全文を読む スポンサード リンク
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