Читать книгу The Form Within - Karl H Pribram - Страница 24

In order to explore directly Köhler’s hypothesis that DC brain activity is involved in perception, I created electrical disturbances by implanting an irritant in the visual cortex of monkeys. To create the irritation, I filled small silver discs with “amphogel,” aluminum hydroxide cream, a popular medication used for peptic ulcers at the time. I then placed a dozen of the discs onto the visual cortex of each of the monkeys’ two hemispheres. Amphogel (or alternatively, penicillin), when applied to the brain cortex, produces electrical disturbances similar to those that initiate epileptic seizures—large slow waves and “spikes”—a total disruption of the normal EEG patterns. I tested the monkeys’ ability to distinguish very fine horizontal lines from fine vertical lines. I expected that, once the electrical recordings from the monkeys’ visual cortex indicated that electrical “seizures” had commenced, the monkeys’ ability to distinguish the lines would be impaired or even totally lost.

Contrary to my expectation, the monkeys were able to distinguish the lines and performed the task without any deficiency. They were able to “perceive”—that is, to distinguish whether the lines were vertical or horizontal”—even though the normal pattern of electrical waves recorded from their brains had been disrupted. Therefore, “geometric isomorphism”—the matching of the internal shape of electrical brain activity to an external form”—did not explain what was happening in the brain, at least with respect to visual perception.

I told Köhler of my results. “Now that you have disproved not only my theory of cortical function in perception, but everyone else’s as well, what are you going to do?” he asked. I answered, “I’ll keep my mouth shut.”

And indeed, since I had no answer to explain my results, when, two years later, I transferred from Yale to Stanford University, I declined to teach a course on brain mechanisms in sensation and perception. I had to wait a few years for a more constructive answer to the problem.