Definition of "diencephalon" []

• The posterior part of the forebrain that connects the midbrain with the cerebral hemispheres, encloses the third ventricle, and contains the thalamus and hypothalamus. Also called betweenbrain, interbrain, thalamencephalon. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The anterior part of the fore-brain, including the rudiments of the cerebral hemispheres, is named the telencephalon, and its posterior portion is termed the diencephalon; both of these contribute to the formation of the third ventricle."
• "It has been carpeted over by the cerebrum, but it is there, deep within the forebrain, and consists of the limbic lobe, the hypothalamus, and, perhaps, other organs of the diencephalon."
• "For reasons of its own, evolution allowed mammalian energy to hold sway, and the recently developed human midbrain or mesencephalon, which had folded over the old diencephalon, could be accurately labeled a mammal brain."