basal ganglion

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

• noun Any of several masses of gray matter embedded in the cerebral hemispheres that are involved in the regulation of voluntary movement.

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

• noun neuroanatomy Any of a group of nuclei in the brain interconnected with the cerebral cortex, thalamus and brainstem

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

• noun any of several masses of subcortical grey matter at the base of each cerebral hemisphere that seem to be involved in the regulation of voluntary movement