# Thalamus The thalamus (from the greek word thalami, meaning "chamber") is a large mass of gray matter on the lateral walls of the third ventricle. It forms the dorsal part of the diencephalon, a division of the forebrain. From Wikipedia: > Nerve fibers project out of the thalamus to the cerebral cortex in all directions, known as the thalamocortical radiations, allowing hub-like exchanges of information. It has several functions, such as the relaying of sensory and motor signals to the cerebral cortex and the regulation of consciousness, sleep, and alertness.