Claustrum

The claustrum is a thin, irregular, curved sheet of gray matter located beneath the inner surface of the neocortex in each cerebral hemisphere. It lies deep to the insular cortex laterally and superficial to the putamen.

It is bordered on both sides by white matter tracts: the extreme capsule (lying between the insular cortex and claustrum) and the external capsule (lying between the claustrum and putamen)

Key arrangement

From lateral to medial, the key arrangement is:

Insular cortex → extreme capsule → claustrum → external capsule → putamen.

Afferent and efferent connectivity

Claustrum has extensive reciprocal connections with multiple cortical regions, including motor, premotor, prefrontal, cingulate, somatosensory, auditory, prepiriform, entorhinal, parieto-occipital, and temporal cortices.

In addition to the neocortex, the claustrum projects to the hippocampus, amygdala, and caudate nucleus.

Proposed functions

Although its precise function remains incompletely understood, Crick and Koch (2005) propose that the claustrum serves as a central hub for multisensory binding and conscious integration. Functioning analogously to an orchestral conductor, it coordinates activity across disparate cortical areas to bind diverse perceptual attributes—such as color, motion, sound, and texture—into a unified, coherent conscious experience. This global integration is thought to rely on high-frequency (30–70 Hz gamma-band) rhythmic synchrony among far-flung cortical assemblies, facilitated by specialized intra-claustral mechanisms such as electrical gap junctions between aspiny interneurons, extensive axonal arbors, or dendro-dendritic synapses.