cerebral cortex

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The extensive outer layer of gray matter of the cerebral hemispheres, largely responsible for higher brain functions, including sensation, voluntary muscle movement, thought, reasoning, and memory.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun neuroanatomy The grey, folded, outermost layer of the cerebrum that is responsible for higher brain processes such as sensation, voluntary muscle movement, thought, reasoning, and memory.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum