THE PARABLE OF THE HEMISPHERES

By John A. Woods
Copyright (c) 1998 by John A. Woods, All rights reserved.

Man's relationship to his self and to others—his behavior as a social being—is all determined ultimately by the way his brain functions.

Jonas Salk
From Man Unfolding

The world we're in the process of creating for ourselves and future generations is the product of our brains; therefore only by understanding how our brains work, can we hope to achieve the insights regarding individual and species motivation.

Richard Restak
From The Brain: The Last Frontier

In Egypt, however, the serpent was the symbol for duality or, more accurately, for the power that results in duality. And that power is itself dual in aspect; it is simultaneously creative and destructive: creative in the sense that multiplicity is created out of unity, destructive in the sense that creation represents the rupture of the perfection of the absolute.

John Anthony West
From Serpent in the Sky The High Wisdom of Ancient Egypt

PARABLES

A parable is a story told to convey a point that is better made indirectly than directly. It usually works by relating a situation with which the listener can empathize and gain insight into him or herself. This paper is a kind of parable. It seems to be about how the brain processes information, but it is really about you and me and how we work to get along in the world. For the parable to work, it is necessary that you to put yourself in the position of those subjects whose reactions on various tests have supplied the clues by which our brains are beginning to understand themselves. Imagine it is you responding to the scientists. Learn what you can and cannot do when your brain is affected in one way or another.

Be aware as you take this perspective that there are two kinds of information for you to consider as you read about these aspects of brain function. One is the results of the research presented here, and one is your own personal experience of this material as you read it. Both are valid examples of how the brain works to help us deal with the world in which we exist as we learn, negotiate within, and ponder what we and this world are all about. If you begin to see how these two kinds of information are interconnected, calling this paper a parable will have made sense for both of us.

BRAINS

Besides the convolutions of its surface, the other most notable aspect of the human cerebral cortex is its duality. It consists of two halves that are nearly mirror images of each other. Though we cannot see our brain, it is easy enough to experience these two halves or hemispheres. Simply hold your two hands in front of you and move them around. They feel different from each other. This is because each is connected to and primarily directed by a different hemisphere.

Every body part outside the brain is represented in the brain. But the left half of the body is mostly represented in the right hemisphere and the right half of the body in the left hemisphere. This means, for example, that the left hand is sensed and directed by the right half of the brain and vice versa for the right hand. There is a direct relationship between every part of the body and the brain. If a certain part of the brain is lesioned (injured), as may happen in a stroke, a body part connected to the lesioned part may cease to function, or not function under any conscious control. For example, if there is an injury to a section of the left hemisphere in which the right arm is connected, that arm will no longer function in a purposeful fashion. And if that injury is severe enough, the existence of the arm itself may be totally out of the person's consciousness, at least in any conventional way. All this is true despite the fact that, physically, the arm is no different from how it was prior to the injury.

Phantom Limbs
A common phenomenon among amputees is the phantom limb. In the loss of a leg, for example, the individual will still feel the leg even though it is no longer a part of the body. The brain circuits that represent the limb are still functioning, and it is difficult for the amputee to shake the idea that the leg is no longer there. In one story, a researcher tells of a patient with a phantom hand that seemed bunched up painfully complained, "The doctor forgot to straighten out my fingers before he took my arm off."¹ Like the arm that exists without representation in an injured brain, the brain circuits that exist in the phantom limb patients have no function when the limb is gone. In other words, for arms to have meaning, they must be represented in our brains, and for a certain part of our brains to have meaning, we must have arms. Without these two parts and the relationship carried with it, purposeful utility of both body parts is irretrievably lost. Whether we realize it or not, it is not possible to consider arm or any body part without, at the exact same time, considering brain.

But what of the brain itself? Isn't it a body part, too? Can a brain function without a brain? Is this a reason for two hemispheres—does the functioning of one provide for the meaningful functioning of the other? The two hemispheres are connected by an extensive band of nerve fibers called the corpus callosum. These fibers connect exact corresponding sections of the hemispheres, so what one brain half is sensing is immediately known to the other. Like the connections between the hand and the brain, for example, there is a corresponding and simultaneous relationship between the two hemispheres.

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