from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun The posterior part of the forebrain that connects the midbrain with the cerebral hemispheres, encloses the third ventricle, and contains the thalamus and hypothalamus.
from The Century Dictionary.
- noun In anatomy, the inter-brain or middle brain, otherwise known as the deutencephalon and thalamencephalon.
from the GNU version of the Collaborative International Dictionary of English.
- noun (Anat.) The interbrain or thalamencephalon; -- sometimes abbreviated to dien. See
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun neuroanatomy The region of the human
brain, specifically the human forebrain, that includes the thalamus, the hypothalamus, the epithalamus, the prethalamus or subthalamus, and the pretectum.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- noun the posterior division of the forebrain; connects the cerebral hemispheres with the mesencephalon
from The American Heritage® Dictionary of the English Language, 4th Edition
from Wiktionary, Creative Commons Attribution/Share-Alike License
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.
If I had thought, by observing the effects of artificial electrical stimuli in small doses on some dozen or so experimental animals with altogether some hundred points of stimulation distributed over the diencephalon, to achieve in due course the looked-for elucidation, then the first result was a thorough disappointment.
On the other hand it is correct that one is dealing with a protective function controlled from the diencephalon, which avoids exhaustion and produces the conditions for an undisturbed recovery.
In this way, for example, we can understand the experimental finding, that in many cases where the stimulus applied to the diencephalon causes defaecation, this is not brought about simply by peristalsis of the colon and rectum.
According to this view of how the diencephalon plays a decisive role in activity which progresses from the part to the whole, it will come as no surprise if still other observations could be made which lead in another direction.
Controls issue from the diencephalon which harness the functional capacities of individual organs in viable responses.
One thing had nevertheless become clear, namely that the parts of the brain communicating directly with the spinal cord at the upper end - the medulla oblongata, and the segment lying directly beneath the cerebrum, the so-called diencephalon - exert a decisive influence on the vegetative controlling mechanisms.
Functionally, the total behaviour of the animal illustrates the fact that, in the part of the diencephalon indicated, a meaningful association of physiological processes takes place, which is related on the one hand to the regulation of the internal organs, and on the other involves the functions directed outwards towards the environment.