Shufflebrain

It's not that the visual cortex and the tectum (or the Wulst) aren't important. And it's not that the vision of a squid is identical to yours and mine. The fact is that we really can't assign all vision to a single anatomical system. We can relate specific features of visual perception to certain structures in particular organisms. But we can't generalize. And if we can't generalize, we can't theorize. Which leaves mind-brain open to the holist--or the magician.

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I can't think of anyone who has contributed more to our knowledge of functional human neuroanatomy than the late Wilder Penfield. Yet the mind-brain question eventually forced him into mysticism. A neurosurgeon who began his career early in this century, Penfield developed and made routine the practice of exploring and mapping a region of the brain before cutting into it. Good doctor that he was, he was preoccupied by the question of whether the treatment would be worse than the disease.

The cerebrum doesn't sense pain directly. Painful sensations from inside the skull travel on branches of peripheral nerves. These nerve fibers actually leave the skull, join their parent trunks, reenter the cranium, and fuse into the brainstem, the lower region of the brain between the cerebrum and spinal cord. Local anesthesia deadens the skull, scalp and coverings of the brain; intracranial surgery can thus be performed on a fully conscious person, which is what Penfield usually did. With electrodes, he stimulated a suspicious area and found out, firsthand, the role it played in his patient's actions and thoughts. In this way, Penfield confirmed many suspected functions and discovered new ones as well.

During the early and middle phases of his career, Penfield was a staunch advocate of the anatomical point of view. In some of his last written words, he related how he had spent his left trying "to prove that brain accounts for the mind." But he had seen too many paradoxes over the years.

Take, for example, a patch of cerebral cortex you're probably using this very moment as your eyes scan this page. The patch is the size of a postage stamp, on the rear of your frontal lobe, about where a Viking's horn emerges from the side of his helmet. It's in a place called area 8 alpha, beta, gamma; or, alternatively, the frontal eye fields; or just plain area 8 for short. Penfield explored area 8 with electrodes and found that it is indeed associated with voluntary eye movements. What do you suppose happens if area 8 is cut out? The person may lose the ability to move his or her eyes, willfully, toward the opposite side of the head (smooth, involuntary eye movements are handled by the occipital lobes). But the voluntary eye movements usually return a few days after surgery. And sometimes the function doesn't disappear at all.

Memory is even more puzzling. Penfield could often elicit vivid recollections of scenes from his patient's distant past by stimulating the temporal lobe. Had Penfield tapped the seat of long-term memory? Removal of the area frequently had no demonstrable effect on the person's memory.

For Penfield, the discrepancies eventually became overwhelming. Shortly before he died, he came to the conclusion that "our being consists of two fundamental elements."[10] For him, those elements had become "brain and mind" (my italics). Even the most faithful of the faithful have had trouble with mind-brain.

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Holism does not rest its case on the structuralist's dubious dialectical position, but on prima facie evidence from some of the finest research ever conducted in psychology or biology--thirty furious years of exhaustive, imaginative, and carefully controlled laboratory investigations by Karl Lashley, the founder of the entire field of physiological psychology.

Lashley investigated memory in a wide variety of species, ranging from cockroaches to chimpanzees. But his favorite subject was the rat. His basic experiment was to train an animal to run a maze. Then he would injure the animal's brain at a particular location and in a specific amount. Finally, he would retest the animal's ability to run the maze postoperatively, comparing its performance with that of control rats whose skulls had been opened but whose brains hadn't been injured.