Claustrum

CLAUSTRUM (Latin - fence), a collection of gray matter located in the cerebral hemispheres between the external capsule, which separates it from the lenticular nucleus, and the extreme capsule, which separates it from the cortex of Reil's insula. The claustrum is formed by small cellular elements of various shapes: fibers from the external and extreme capsules end in it. The significance of this formation is disputed: some classify it as part of the basal ganglia; others consider it as a detached part of the sixth layer of Reil's insular cortex due to the passage of the extreme capsule here. Finally, a third group denies its belonging either to the cortex of Reil's insula or to the basal ganglia, but considers it as a completely independent (sui generis) formation, citing the following arguments in favor of their opinion: the cortex of Reil's insula has all six layers without the claustrum; embryologically, the inner layers of the insular cortex have nothing in common with the claustrum; the claustrum is separated from the cortex not only by the extreme capsule but also by the uncinate fasciculus; the cells of the claustrum do not resemble the cells of the sixth layer in shape. Due to the deep location and small size of the claustrum, its physiology and pathology have not yet been clarified.