Or gray matter; Fissured outer layer of the cerebrum. Some 3 mm thick in the adult, it is the most sophisticated part of the brain, responsible for all higher functions and for initiating voluntary movement. Anatomists divide it into four lobes, named for the skull plates beneath which they lie: frontal, parietal, temporal and occipital.
The layer of unmyelinated neurons (the gray matter) forming the cortex of the cerebrum; SYN. cerebral mantle, pallium, cortex.