The Corpus Callosum (Latin for hard body), along with the Anterior and Hippocampal Commissures; keep the two hemispheres acting as a unit. It is the anatomical structure which is responsible for providing the major connections of the the two hemispheres in a point-to-point or Topographic manner.
The design of the human nervous system is such that each cerebral hemisphere receives information primarily from the opposite half of the body. This
'Contralateral Rule', with the exception of olfaction, applies to vision and hearing, as well as to body movement and touch (Somatic sensory) sensation. It is the Corpus Callosum that integrates hemispheric activity by updating each hemisphere regarding information received by the other and perhaps by suppressing one hemisphere while the other takes over some activity.
The Zipper Hypothesis
is a prominent working hypothesis concerning collosal function. It aserts that the Corpus Callosum knits together the representations of the midpoints of the body and spaces that are divided by the longitudinal fissure of the brain. 
A closer examination of brain activity reveals four possible neurophysiological roles for the Corpus Callosum:
Two involving the reduction of neural activity (inhibition) in part of (topographic), or all of the hemisphere, and
Two involving the increase of neural activity (excitation) in part of (topographic), or all of the hemisphere opposite to where the activity originated.
It is inconceivable that a nerve fiber tract as large as the Corpus Callosum simply serves to shut down one entire hemisphere while the other is active. In fact, there is no electrophysiological or metabolic evidence that there is any suppression of overall activity in one hemisphere as the other becomes more active.
Topographical Inhibition
does not mean an absence of information. As a matter of fact, topographical inhibition can result in the activation of complementary aspects of almost any function in the two hemispheres. Research has shown that arousal and attentional mechanism located within the brain tend to activate regions of both hemispheres symmetrically. The brain's main arousal system, The Reticular Activating System, does in fact consist of subcortical groups of cell bodies and pathways that are not separated by commissurotomy.
An additional fact is that related aspects of some item in memory are represented in the brain anatomically near each other, or at least that access to these related aspects is provided by neighboring neurons.
Topographic inhibition across the Corpus Callosum suppresses in one hemisphere the exact same neuronal pattern of activity (or Neural Network), that originated in the other while simultaneously allowing activity to develop in surrounding neurons representing complementary (or contextual), aspects of the original infromation.
In most language-related activity, for example, it would be excitation in the Left Hemisphere (Wernicke's Area) that inhibits the equivalent neural network in the Right Hemisphere and concomitantly promotes its surrounding context-associated processing.
As an example, excitation of the cortical neurons that represent 'falcon' in the left hemisphere would inhibit 'falcon' in the right hemisphere while allowing excitation of the peripheral falcon-related neural networks ('hawk, owl, eagle,'etc.), in that hemishpere. If the ongonig language is, 'The majestic peregrine falcon may attain speeds up to 200 mph in pursuit of its avian quarry - the pigeon!' then not only would individual words produce related contexual items in the right hemisphere but also the meaning of the left hemisphere's sentence, as a whole, would generate right hemispheric contextual meaning.
Where, 'The majestic peregrine falcon may attain speeds up to 200 mph in pursuit of its avian quarry - the pigeon!' denotes a specific act of predation, the pattern in the right hemisphere would be inhibition of that specific act of predation (falcon and pigeon), but excitation of classes of similar predator-prey relationships; cannoting the dominance of the strong over the weak, the fast over the slow, the surprise and disperation of the attack, etc.
These complementary aspects of whatever item is being processed are the result of a mirror-image negative relationship between equivalent areas of the two hemispheres, created or at least accentuated by continuous topographic inhibition across the cerebral commissures.
In the case of language, this implies that whatever the left hemisphere asserts explicitly, the right hemisphere cannotes in a more generalized pattern with the explicit message omitted. Thus, by producing two distinctly different patterns of neural excitation (or Neuronal Connectivity), within bilaterally identical regions (each of which was aroused by the general attention system), Collosal Homoptic Inhibition allows the two hemispheres momentarily to hold different perspectives on the same information.
This concept of complementary functions of equivalent areas of the two hemispheres is not limited to the language-related processes, but applies to other functions including perception where, for example, perception of a visual figure versus its contextual background also operates in a like fashion.
There is a clear relationship between the two different patterns of Neuronal Connectivity and the specialized functions of the two Cerebral Hemispheres. Both vertical and horizontal circuitry in the two hemispheres have been well documented by Neurophysiologists. There is a striking parallel between alternative modes of memory storage and the kinds of processing horizontal and vertical neuronal connections provide. Two theoretically different ways of storage that seem relatable to anatomical processes are "Conjunctive Encoding" and "Coarse Encoding."
Conjunctive Encoding
uses a separate definite unit of memory or memory engram (Neural Network) to stand for every aspect and every important relationship (conjunction) between items, this type of encoding pattern is highly specific but it quickly runs our of units.
Coarse Encoding
is a mechanism in which each Neural Network of memory is broadly tuned so that properties of features specified by a Network overlap in varying degrees with those specified by other Networks. Any part or feature of, say, a visually presented item, is then represented by activity in a group of Networks within whose overlapping representational boundaries it falls. Although efficient and quite flexible in terms of situations it can approximately code, coarse encoding has its limitations. A coarse encoding system breaks down when it has to encode large numbers of highly similar, co-occurrent events.
The class of cells called Double-Bouquet cells to which the Corpus Callosum projects, mediate the relative dominance of vertical and horizontal circuitry in favor of the latter!
There is however, a constant vying for control between the hemispheres. Hemispheric activation does not depend on a hemisphere's real aptitude or even on its actual processing strategy on a given occasion, but rather on what it thinks it can do.
«There are always two forces warring against each other deep within the Mind. One force tells us to do those things we should not; while the other urges us to do those things we should, those things that seem the most difficult!»
Although each hemisphere is exposed to the same sensory input, inhibition of information transfer takes place when the information received is contradictory; precipitating Psychological Conflict !
The Left Hemisphere will attend to the verbal cues, and the Right Hemisphere will attend to the nonverbal Analogical cues. During such moments of conflict, the Left Hemisphere alone governs consciousness. Mental events in the Right Hemisphere, however, will continue a life of their own and act as a
'Freudian Unconscious' - as an 'independent resevoir of inaccessible cognition', which may create seemingly inappropriate behavior and/or emotional states in an individual.
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