Obituary: Professor Roger Sperry

Roger Wolcott Sperry, neurobiologist: born Hartford, Connecticut 20 August 1913; Researcher, Harvard University 1941-46; Assistant Professor of Anatomy, University of Chicago 1946-53; Hixon Professor of Psychobiology, California Institute of Technology 1954-84 (Emeritus); Wolf Prize in Medicine 1972; Nobel Prize for Medicine and Physiology 1981; National Medal of Science 1989; married 1949 Norma Deupree (one son, one daughter); died Pasadena, California 17 April 1994.

WHEN Roger Sperry won the Nobel Prize for Medicine and Physiology in 1981, his students and colleagues had two questions. The first was: which of his contributions did he win the prize for? Sperry's research had revolutionised two separate fields of neuroscience, shifting scientists' thoughts about the way the brain works and the way that nerves link together in the embryo. The second question was: where on earth was Sperry? An intensely private person who loved the outdoors, Sperry was touring the rugged Mexican coastline at the time, and it was in perfect character for him to continue his vacation incommunicado when he heard of the award on the radio. Members of his laboratory hung a 'Gone Fishing' sign on his office door and fielded reporters for over a week until their mentor

resurfaced.

At the time of his death, Sperry was an emeritus professor of the California Institute of Technology (Caltech), where he had worked since 1954. It was here that he performed the split-brain studies that won him his Nobel Prize, which was shared with the neuroscientists David Hubel and Torsten Wiesel of Harvard University, who were working on studies unconnected with Sperry's.

Sperry was born in Hartford, Connecticut, in 1913. He received his undergraduate degree in English Literature from Oberlin College, Ohio, in 1935, followed by a Masters degree in psychology in 1937, also from Oberlin. After earning his PhD in zoology from the University of Chicago, he held academic positions at Harvard University and at Chicago. In 1954, he became the Hixon Professor of Psychobiology at Caltech, retiring in 1984.

Before Sperry's experiments, neuroscientists believed that the left side of the brain dominated the right. Sperry's work, which began in cats and monkeys, culminated in a spectacular series of studies in human beings, showing that each hemisphere of the brain has its own consciousness and expertise.

The left, for instance, excels at language, mathematical and analytical skills, while the right is superior at spatial skills and at recognising objects. The experiments also demonstrated that the corpus callosum - a bundle of 200 million nerve fibres that links the hemispheres - is essential for proper information flow between the brain's two halves.

Sperry's human studies took advantage of a novel operation performed to halt serious epileptic fits. Surgeons would slice through the corpus callosum, isolating each hemisphere from the other. Though such split-brain people could function well, Sperry uncovered intriguing deficits. A blindfolded patient, for instance, was unable to say 'book' when a book was placed in his left hand - even though he could later select the book from a trayful of objects. In other words, the right hemisphere - which controls the left hand - could recognise an object, but could not describe it verbally.

Sperry's split-brain work captured the popular imagination, spawning a mountain of books and articles about 'right-brain' and 'left-brain' thinking. But his earlier work, on nerve cell development, was equally, if not more, important. It spoke to a fundamental question in neurobiology: How do our brain's billions of nerve cells come together to form the right

circuitry?

The prevailing view in the 1940s was that there was nothing special about any particular nerve, and that cells forged their precise connections in the brain through trial and error. Sperry showed otherwise. By severing the optic nerve of a newt, he demonstrated that the nerves could grow back to their original target in the retina - even when he rotated the newt's eyeball by 180 degrees. To explain his findings Sperry hypothesised that nerve cells are covered with unique chemical identity tags that direct them to make the right connections. The search for these chemical tags continues fast and furious today.

From the 1960s onward, Sperry turned his efforts to a thornier problem: an understanding of the mind, and of consciousness. Consciousness, Sperry held, is something larger than a simple sum of all the nerves, chemicals and electrical impulses in the brain. He also argued that consciousness profoundly influences the chemical workings of our brains. Although Sperry's theories in this arena were less readily embraced by his colleagues, it is for this body of work that he wished to be remembered.

Sperry was by all accounts a quiet, retiring man, who sculpted, fished and collected fossils avidly - he owned, among countless specimens, the second largest ammonite fossil in the world. Despite suffering from a degenerative neuromuscular disease for the past 20 years, he was still dictating manuscripts a week before his death. His work's final focus was on building an ethical framework for science.

'Sperry was always interested in the great intellectual questions and he was remarkably successful at attacking them,' John Allman, Professor of Psychobiology at Caltech, said. 'He was certainly one of the great figures of modern science.'

(Photograph omitted)