The claustrum of the brain is a thin, irregular sheet of gray matter located deep within the brain, between the insula and the putamen. It is part of the telencephalon (forebrain) and is present in both hemispheres.

Composition of the Claustrum:

1. Neurons:
   • Mostly GABAergic inhibitory neurons (using GABA as a neurotransmitter).
   • Some glutamatergic excitatory neurons.
   • These neurons are highly interconnected and send projections to many areas of the cerebral cortex.
2. Glial cells:
   • Supporting cells that help with nutrient supply, immune defense, and maintaining the brain’s environment.
3. Extracellular matrix:
   • A supportive network that provides structural integrity and biochemical signaling.

Summary:

The claustrum is made of gray matter, which consists mainly of neuronal cell bodies, dendrites, glial cells, and unmyelinated axons. It is believed to play a role in consciousness, attention, and coordination of information across different parts of the brain, although its exact function is still being studied.

Let me know if you want a diagram or illustration of it.