Why They Won Nobel Prizes

"Sometimes I think we are more explorers of an unknown continent that we are physicians or scientists," Torsten N. Wiesel, Winthrop Professor of Neurobiology, says quietly. That continent is the brain, and the 22 years of research Wiesel calls only the "first steps" in its exploration have won him and colleague David H. Hubel, Berry Professor of Neurobiology, the 1981 Nobel Prize for Medicine.

A research team since 1959, Hubel and Wiesel have studied the workings of the cerebral cortex's visual region, only a small part of the organ Wiesel terms "the most complicated machine on earth."

Yet Hubel and Wiesel's knowledge of the way the brain processes information from the eye advances the study of the full cortex--10 billion neurons folded together at the brain's crust that may be the key to man's development over other animals.

The goal is to understand how images from the eye are translated in the visual cortex to the language of the brain, Hubel says. The dream is to map the machinery of the mind.

"I have always believed that psychology must be a branch of biology," he says, "though some psychologists would disagree with me. The 'mind' is merely an abstraction," while the brain--in some biologically definable way-- comprises human thought.

In search of what they call the "neural substrate," the two researchers began implanting sensitive electrodes into the brains of anesthetized monkeys. The electrodes monitored individual cell responses from within the visual cortex; in a laborious process, Hubel and Wiesel tested the reaction of specific cells in specific areas of the visual cortex to the specific images placed before a monkey's eyes.

The apparatus was simply a slide show for the anesthetized monkeys. The knowledge of which cells would send out electrical impulses in response to--or "recognition" of--which visual patterns could offer a map of the architecture of the visual cortex.

The breakthrough came in what both Hubel and Wiesel say was an accident. The cells of the monkey's visual cortex failed to "recognize" white dots on the screen, but reacted regularly while the researchers were changing slides. "It wasn't the dot at all, but the edge of the glass" on moving slides, Hubel says.

The team took months to convince themselves that edges and lines caused the reactions in the cells. A newspaper or television picture is made up of tiny dots. But Hubel and Wiesel found that the visual cortex breaks objects down, not into dots, but into line segments.

As the mapping process continued, now with slides of lines and bars, the two discovered that different cells within the region are specialized, recognizing only certain images. Certain cells responded optimally to a bar or edge of light with a particular orientation along the visual axis. And more complex cells seemed to recognize more complex images passed on by several simpler cells.

"Each of these cells in the cortex is looking out of a pinhole to the world," Wiesel says, "only at later stages combining into a whole."

And while cells on either side of the brain responded preferentially to one eye over the other, more than half received input from both eyes. The upshot was a neurological sense of how and where the two separate retinal images are unified in the brain.

The overall primary visual cortex, Hubel and Wiesel discovered, is composed of two systems of columns. One groups together cells recognizing steadily changing angles of orientation of bars and edges, while the other holds cells with the same eye preference. This architecture has since been found all along the cortex, even in areas having functions which are still unknown.

"All this wasn't just a mysterious current moving through the brain," Wiesel says, "but a very, very precisely wired machine."

Though it is a vision that might disturb some, Hubel welcomes it. "A lot of philosophical questions can be bypassed," Hubel says. Terms like "the mind" or "free will," he adds, are "not valuable in the context of science."

"We do have free will," he says, but it is biologically based: "It's one's ability to respond to things of greater and greater abstraction."

A biologically based understanding of the brain "may influence our whole philosophy so that we don't think in such a mystical way," he adds.

According to Hubel and Wiesel, their findings also shed light on the classic question of "nature vs. nurture"--whether perception and behavior are instinctive or learned in the environment. Since specific cells naturally recognize simple shapes, "it seems that at birth you are endowed with an eye for details," Wiesel says, adding, "The neuroconnectors are there."

"If you don't nurture these connection between the eye and visual cortex properly," if they are not used within a "critical period after birth, they will be lost," Wiesel says.

That discovery may aid the prevention of childhood blindness. And Wiesel says the idea of a "critical period" could perhaps apply to much more complicated brain function. "Deprivation of attention, emotion, what a mother provides for a child, emotional contact with siblings--there is evidence that kids lacking these things develop more slowly," he explains, adding, "Perhaps it is important to stimulate people to use their intellectual and emotional resources early."

Ultimately, Hubel says, knowledge of the brain "may help us to learn how to control our behavior, how to educate ourselves."

Or maybe it won't. Wiesel cautions that scientists may never fully understand the brain. "We may not be able to pinpoint all the solutions so clearly. At this stage we are only defining the variables," he says, adding, "The most exciting work is ahead of us."

But also ahead for Hubel and Wiesel is a December trip to Stockholm, for Nobel lectures and award ceremonies. "I don't think [the prize] means anything. I don't take it seriously," the Swedish-born and educated Wiesel says.

"I look forward to when I can stop doing press conferences and interviews and get back to doing experiments," he adds.