Sperry Roger Wolcott
SPERRY ROGER WOLCOTT
(b. Hartford, Connecticut, 20 August 1913; d. Pasadena, California, 17 April 1994), psychobiology, functions of the hemispheres of the human brain, chemoaffinity hypothesis of neuron growth, cognitive neuroscience.
Sperry shared the Nobel Prize in the category of Physiology or Medicine in 1981 for clarifying the functions of the two hemispheres of the human brain. Before Sperry’s time, the brain’s left hemisphere was generally seen as dominant and the right hemisphere as making relatively minor contributions. Sperry’s research involving patients with “split” brains—brains with surgical division of the corpus callosum and frontal commisures—showed instead that the hemispheres have complementary functions, with the left hemisphere specializing in language and the right hemisphere excelling in visual perception and related processes. This research contributed to the development of a new field of cognitive neuroscience and to the cognitive revolution in psychology in the 1960s. Sperry also advocated a new perspective on the mind–brain relationship in which the mind was conceived as an emergent phenomenon that exerted causal influence on the brain. (He denied that this view implied any dualism.) In this way Sperry’s work built a bridge between the formerly separate “two cultures” of science and the humanities. His earlier research on neurophysiology elaborated a chemoaffinity hypothesis in which the growth and function of neurons was viewed as largely prewired and under genetic control rather than being mechanical and somewhat random with connections functionally determined.
Early Development Roger Sperry grew up as a relatively shy child in rural Connecticut with an early interest in biological topics. In grade school he collected and raised moths. At junior high school age, he showed a continued interest in animals, including trapping and acquiring wild animals as pets. These interests prefigured his later research activities, many of which involved fish, frogs, lizards, rats, cats, and monkeys, as well as humans. As an adult he continued pursuing his youthful interests in boating, fishing, diving, and collecting fossils. In his brief Nobel autobiographical sketch, Sperry mentioned that he had been a letterman in three sports in high school and college—his skills in baseball, basketball, and track perhaps showing not only a concern for high achievement but also an intense focus on the potentialities of the human body. He attended Oberlin College in Ohio on an athletic scholarship.
At Oberlin, Sperry majored in English literature and received his bachelor of arts degree in 1935. His choice of a major was related to his lifelong concern with clarity of written expression. (During the rest of his life he spent much time writing, revising, and editing his scientific manuscripts and those of his students.) His undergraduate major also represented a commitment to the arts and humanities, and as an adult Sperry continued to engage in such activities as sculpture, ceramics, drawing, water colors, and folk dancing. He continued his studies at Oberlin and received a master’s degree in psychology in 1937 under R. H. Stetson; for the rest of his career he identified to some extent with the field of psychology.
Sperry went on to the University of Chicago, where he completed a PhD in 1941 in zoology under Paul Weiss, a scientist well-known for research on the nervous system of amphibians. This time—the late 1930s and early 1940s—was an era of behaviorism in American psychology and related areas of neurology. It was thought that the growth of neurons was controlled mainly by mechanical factors and was a somewhat random process. The ultimate function of a nerve was supposed to be influenced functionally by whatever end structures it happened to innervate. For example, Weiss implanted a supernumerary leg onto the body of a salamander and showed that it functioned normally despite the fact that it was innervated by nerves that did not normally connect to a leg.
Sperry’s own research often seemed to have the opposite implications. If he implanted motor nerves into the “wrong” muscles of a rat’s leg, the leg continued to function incorrectly throughout the animal’s life, with no functional adaptation. The same was true of sensory nerves. Many years later, Sperry transferred skin from a frog’s belly (together with its nerve supply) to the animal’s back, and skin from the back to the belly. From that time onward, whenever the animal’s belly was stimulated, it scratched its back, and vice versa, with no readjustment of function resulting from experience. In other subsequent research Sperry cut the optic nerve of a goldfish and reim-planted the eye rotated 180 degrees. The parts of the nerve grew back into the brain of this fish (its optic tectum) in precisely the same locations as before, even though they had to cross over other possible sites to do so. It was as if the nerves were guided by some kind of precise chemical markers directly to their destinations (though the exact chemicals hypothesized to do this have still not been identified). After the fish recovered from this surgery, its visual orientation to prey remained 180 degrees out of phase. When a morsel of food was located on the left, the fish would swim to the right, and vice versa. No functional readaptation of this response occurred during the remainder of the life of the fish, and if it had not been fed artificially, it would have starved.
Postdoctoral Work After completing his PhD in 1941, Sperry did a year of postdoctoral work under psychologist Karl S. Lashley of Harvard University. He continued to work with Lashley from 1942 to 1946 as a biology research fellow at the Yerkes Laboratories of Primate Biology in Orange Park, Florida. In 1942–1945 he also met his military obligations by working on the government’s Medical Research Project on Nerve Injuries. Much like his doctoral supervisor, Weiss, Sperry’s postdoctoral mentor Lashley was known as a behaviorist who endorsed functional views of the central nervous system. Lashley had carried out extensive studies of the effects of brain lesions on rats’ maze performance, searching for the location of the neurophysiological substrate of memory (the engram). Lashley’s work had found little evidence that the location of such brain lesions was significant. Instead, what seemed to be important was simply the amount of brain tissue destroyed. Once more, Sperry’s work seemed to have somewhat the opposite implications, strongly supporting the importance of hard-wired, specific neurological connections. For example, when Sperry attached the neurons of monkeys to the “wrong” muscles of their arms, their motor activities with these limbs became permanently abnormal. However, unlike fish, frogs, or rats, these monkeys seemed to be aware that something was wrong with their arms and tried their best to correct their movements by conscious efforts. At first, these efforts simply took the form of suppressing the abnormal movements caused by the incorrect neurological connections that had been surgically imposed.
University of Chicago After completing his postdoctoral work, Sperry returned to the University of Chicago as an assistant professor of anatomy from 1946 to 1952. At Chicago his research continued to address “big” issues, leaving minor technical matters to other scientists. Sometime before 1950, Sperry’s career was disrupted by tuberculosis. In an attempt to recover from the disease, he spent time in a sanitorium at Saranac, New York, and in the warmer climates of the Bahamas. It was in this latter location that he met a fellow biologist, Norma G. Deupree; they married in Wichita, Kansas, in 1949.
When Sperry attempted to return to the University of Chicago in 1952 after a leave of absence, the Department of Anatomy was reluctant to reappoint him because with tuberculosis, he was not likely to live very long. Under these circumstances, he took an alternative appointment offered by James Grier Miller, head of the Department of Psychology and Psychiatry, as a tenured associate professor. In 1952–1953, Sperry served as section chief, Neurological Diseases and Blindness, at the National Institutes of Health in Bethesda, Maryland.
California Institute of Technology In 1954 Sperry moved to the California Institute of Technology (Caltech) in Pasadena, where Sperry was appointed the Hixon Professor of Psychobiology. Sperry continued in this position for several decades until his retirement. One topic he addressed during these years was the question of “field” effects in the brain, as hypothesized by Gestalt psychology. Sperry approached this question quite directly. If the brain functions through creating magnetic or other electrical fields (rather than, as conventionally believed, simply by the transmission of impulses by neurons), it should be possible to disrupt such field effects. Sperry introduced various wires and mica chips into the surface of the cerebral cortex to disrupt any such electrical fields but found no effects on neurological function. The burden of proof concerning such electrical fields and their effects was thus placed on Gestalt theorists. To this date they have not tried to counter these findings, and thus their “field” hypothesis remains weakened.
At this time Sperry began the research on “split-brain” animals that eventually led to his Nobel Prize. He began with cats, examining the effect of cutting the optic chiasm and the corpus callosum on their ability to transfer their learning of certain visual patterns from one visual field to another. The split-brain animals were deficient in such transfers. In fact, they could now learn incompatible responses using the separated hemispheres of the brain. The cat might learn to prefer a triangle to a circle in the left visual field but to prefer a circle to a triangle in the right visual field. Sperry continued his work on other split-brain animals, now with monkeys. Research under way at this time by others, such as Robert Patton and his colleagues, went further than simply cutting the corpus callosum and other frontal commisures of primates and actually carried out hemicerebrectomies. Such animals, with only one cerebral hemisphere, were surprisingly normal in their functioning. Of course, they had the expected effects of such massive lesions, such as hemiparesis (paralysis of the arm and leg opposite the hemisphere that was removed) and visual field defects on the side of space opposite to the lesion. But such hemicerebrectomized monkeys performed about as well on discrimination problems as control animals without such surgery. They simply turned their heads to use their “good” visual field and their nonparalyzed hand to pick up the object that was correlated with reward in the experimental problem.
It was at this point that the opportunity to do research with human “split-brain” patients arose for Sperry. Neurosurgeon Joseph E. Bogen cooperated in this work. The patients involved each suffered from intractable epilepsy, so resistant to the usual medical treatments that a procedure as drastic as cutting the corpus callosum and frontal commisures seemed to offer a reasonable hope of limiting the spread of seizures. At the same time, graduate students sophisticated in psychological testing methods, such as Michael Gazzaniga, were available at Caltech to work under Sperry’s direction.
To casual observers, the patients who had their corpus callosum and commisures cut showed remarkably few effects of the procedure. More refined testing procedures were necessary to show its full results. The usual testing procedure was to seat the patient in front of a screen, with a slot in which the hands could be placed underneath it.
Roger Wolcott Sperry . Sperry collects his Nobel Prize in Medicine in Stockholm, for his work on the functional specialization of the cerebral hemispheres, December 10, 1981. HULTON ARCHIVE/GETTY IMAGES.
The patient was asked to fixate on the midline while visual displays were projected to either the left or the right visual field (or both), but too briefly to permit any visual scanning. Under these conditions, it was apparent that the left hemisphere was in charge of speaking. It could name objects projected to the right visual field or presented to the right hand beneath the screen. It was also able to read and interpret sentences presented to the right visual field or to do mathematical calculations with numbers presented there. In contrast, the right hemisphere was mute, unable to understand connected verbal expressions and unable to do arithmetic. However, the right hemisphere was not as helpless as it at first appeared to be. It could direct the behavior of the left hand beneath the screen to indicate in nonverbal ways what it had experienced. In this way the right hemisphere could demonstrate an ability to read and understand single words. Moreover, the right hemisphere was considerably superior to the left in carrying out various visual perceptual tasks with respect to materials presented to the left visual field or to the left hand. Thus, the right hemisphere was better able to copy geometrical figures, to recognize faces, or to build or copy structures with three-dimensional wooden blocks. In interpreting these and other such results, it became evident to researchers that there were essentially two separate conscious beings within one head. (The two hemispheres could function independently of one another, but there is no evidence regarding consciousness in this fact.) This was evidently the type of scientific breakthrough that most impressed the Nobel Committee.
The results of these split-brain studies of Sperry and his colleagues were consistent with and clarified the large existing literature concerning hemisphere differences in the human brain, and they revolutionized scientific views on this topic. For example, studies of dichotic listening with normal subjects had long shown right-ear (and thus left-hemisphere) superiority in repeating words and left-ear (right-hemisphere) superiority in the perception of musical tones. Studies of unilateral cerebral lesions dating back to the time of Paul Broca and Hughlings Jackson in the nineteenth century had long since shown left-hemisphere damage to be associated with aphasia or alexia, while right-hemisphere damage was associated with prosopagnosia (difficulty recognizing faces) and constructional apraxia (difficulty in drawing or building block structures, for example).
During his career at both Chicago and Caltech, Sperry served as a mentor to many doctoral students and postdoctoral fellows. Although he had the reputation of being a lecturer of outstanding scientific clarity, he was always less comfortable in dealing with large groups than in one-to-one conversations with students. As a professor he continued to be a shy, even dour man, albeit one with a twinkle in his eye and a sly grin. He was never one to tell his students what experiments they should run but stood ready with a trenchant critique of any detailed plans they might devise on their own initiative. As stated already, Sperry preferred to work on the “big” issues and let others do the detailed, technical mopping up. He always cautioned students against spending their time on scientific trivia.
Already by the 1960s, Sperry had rejected the idea that brain activity can be accounted for strictly on the basis of physical, chemical, and physiological concepts, with the mind being some kind of epiphenomenon that can safely be disregarded by science. Although he rejected dualism, Sperry came to believe that the mind is an emergent entity that exerts its own causal force downward on the central nervous system and is important in the process of deciding how to act in the world. He used the analogy of a television, where although the concepts of electronics are necessary to understand how it works, they fail utterly to deal with the overarching content of news, drama, or artistic activity seen by viewers. In his view, a baseball game on television is not an activity played to empty benches but one with human purpose, meaning, and value. Science must take such factors into consideration to render an adequate account of brain activity. Providing such an account is one purpose of many researchers in the new field of cognitive neuroscience that Sperry helped to create. Sperry’s views of the mind-brain relationship were controversial when he first voiced them but are less so today. Many researchers in cognitive neuroscience (including the late Francis Crick, who moved into this area as a follow-up to his work on the double helix model of DNA) take the issue of consciousness very seriously.
Roger Sperry died in 1994 at the age of eighty of aspiration pneumonia, a complication of a long-term neuro-muscular disease that had made it impossible in his later years for him to attend the numerous symbolic occasions to which he was invited. He was survived by his wife, Norma, his son, Tad, and his daughter, Jan.
Appendix A of Colwyn Trevarthen, ed., Brain Circuits and Functions of the Mind: Essays in Honor of Roger W. Sperry (Cambridge, U.K.: Cambridge University Press, 1990), contains a list of Sperry’s publications. Archives of his papers exist at the California Institute of Technology and at Oberlin College.
WORKS BY SPERRY
“The Problem of Central Nervous Reorganization after Nerve Regeneration and Muscle Transposition.” Quarterly Review of Biology 20 (1945): 311–369.
“Regulative Factors in the Orderly Growth of Neural Circuits.” Growth Symposium 10 (1951): 63–67.
“Cerebral Organization and Behavior.” Science 133 (1961): 1749–1757.
“Chemoaffinity in the Orderly Growth of Nerve Fiber Patterns and Connections.” Proceedings of the National Academy of Sciences of the U.S.A. 50 (1963): 703–710.
With Michael S. Gazzaniga and J. E. Bogen. “Interhemispheric Relationships: The Neocortical Commisures: Syndromes of Hemisphere Disconnection.” In Handbook of Clinical Neurology, edited by P. J. Vinken and G. W. Bruyn. Vol. 4. Amsterdam: North-Holland Publishing, 1969.
“Lateral Specialization in the Surgically Separated Hemispheres.” In Neurosciences: Third Study Program, edited by Francis O. Schmitt and Frederic G. Worden. Vol. 3. Cambridge, MA: MIT Press, 1974.
“Mind-Brain Interaction: Mentalism, Yes; Dualism, No.” Neuroscience 5 (1980): 651–662.
Bogen, Joseph E. “My Developing Understanding of Roger Wolcott Sperry’s Philosophy.” Neuropsychologia 36 (1998): 1089–1096. Bogen, a neurosurgeon, collaborated with Sperry in the split-brain studies on humans.
Meyer, Ronald L.“Roger Sperry and His Chemoaffinity Hypothesis.” Neuropsychologia36 (1998): 957–980.
Sperry, Norma D.“In Memoriam—Roger Sperry.” Neuropsychologia 36 (1998): 955–956. This article by Roger Sperry’s widow was part of a memorial issue of a scientific journal containing articles by a group of his former students and associates.
Trevarthen, Colwyn, ed. Brain Circuits and Functions of the Mind: Essays in Honor of Roger W. Sperry. Cambridge, U.K.: Cambridge University Press, 1990.
Voneida, Theodore J. “Sperry’s Concept of Mind as an Emergent Property of Brain Function and Its Implications for the Future of Humankind.” Neuropsychologia36 (1998): 1077–1082.
Donald K. Routh