The Man Who Split Our Brains

This is the third in a series of articles that celebrate the lives of the Nobel Prize laureates whose names grace the 100 streets of Laureate Park. These laureates are extraordinary men and women – many of whom are alive today – who through their lifetime achievements have made our daily lives immeasurably richer, often in ways not readily evident. Through these articles, we hope to introduce you to these exceptional individuals and encourage you, perhaps, to learn more about them.

The next time you say to your mother-in-law, “I’m of two minds about that suggestion of yours,” you might give a moment’s thought to Roger Wolcott Sperry, the American neuropsychologist who discovered that we are all quite literally of two minds, on every subject. This is because Sperry found that the two half-moon hemispheres of our brains carry out distinct, discrete functions, and in some cases can operate independently of one another, a discovery for which he won the Nobel Prize in medicine in 1981.

Sperry’s contributions to our knowledge of the human brain were voluminous and far-reaching, but today he is most remembered for his development of the split-brain theory. In recent decades, popular culture has regrettably distorted this theory by pigeonholing individuals into the two categories of analytical “left-brained” scientists and imaginative “right-brained” artists. The brain’s combined functions and their interconnectedness across the two hemispheres, however, tell a more complex story – an inkling of which we will see below.

Born in Hartford, Conn., into a family of modest means, Sperry at an early age exhibited a serious and relentlessly curious character. In the 1940s, after acquiring advanced degrees in psychology and zoology at Oberlin College and the University of Chicago, Sperry pursued postdoctoral research at the secretive Yerkes Laboratories of Primate Biology, then located in Orange Park, Fla. While conducting this wartime research, Sperry postulated in a series of carefully crafted papers that the areas of the brain that perform specific functions are not entirely plastic or interchangeable but mostly hardwired. In one of his early experiments, Sperry severed the optical nerves of amphibians and reconnected them upside down, expecting their brains to compensate to view the world right side up. But the amphibian brains could not adjust, and in their eyes the world remained upside down.

In further experiments with cats in the 1950s, Sperry began to appreciate that mammalian brains were not only hardwired but also asymmetrical. It was already widely known that the right hemisphere controls movement on the left side of our bodies, while the left hemisphere controls bodily motion on our right side. The two halves of the brain, in both humans and animals, are connected by a bundle of nerves, a sort of system of cables, called the corpus callosum, which propels information via neurons between the hemispheres. In his experiments with cats, Sperry severed the corpus callosum and altered the wiring of the cats’ optic nerves so that each eye communicated with only one side of the brain. The goal was to see how a complete separation of the two hemispheres might alter the cats’ behavior. (Although such brain surgery sounds brutal, a cat undergoing this operation would only feel pain at the cutting of the scalp, but none within the brain itself, since brain cells register no pain.) The cats with a severed corpus callosum immediately showed odd behavior. Those wearing a patch on one eye could successfully navigate a maze used for the experiments, but when the patch was applied to the other eye, the cats froze or became lost in the labyrinth. As no information could pass through the corpus callosum, Sperry concluded that each hemisphere of the cats’ brains controlled separate functions.

In 1962, an opportunity arose for Sperry and his team, including the noted neuropsychologist Michael Gazzaniga, to continue this brain research with human subjects. Sperry learned that to reduce the effects of epilepsy, several patients had undergone an operation to sever their corpus callosum. While testing these patients, Sperry and Gazzaniga uncovered further secrets of the two hemispheres’ functions. The patients, for example, could name objects, such as a screwdriver or key, shown to them using solely their left hemisphere but could not name those same objects using their right hemisphere, though they could draw a picture of the objects using their left hand. Thus commenced Sperry’s mapping of the human brain, as he assigned facility with language, numbers, logic, and analytic reasoning to the left hemisphere, and art, creativity, intuition, and holistic thought to the right hemisphere. The two sides of our brains are never fully complete, though, nor do they function optimally without the continuous messaging across the corpus callosum.

So, yes, tell your mother-in-law that you are of two minds about her suggestion. But be aware that she might have read up on Nobel laureate Roger Sperry and know quite well that the two sides of your brain are constantly talking to one another, making them work as one.

Next month: Ada Yonath, the Cheerful Chemist.

Dennis Delehanty moved to Laureate Park with his wife, Elizabeth, from the Washington, D.C., area in mid-2018. Dennis completed a long career in international affairs at the U.S. Postal Service, the United Nations and the U.S. Department of State, jobs that required extensive global travel and the acquisition of foreign languages. You can contact Dennis at donnagha@gmail.com.