Torsten N. Wiesel | Biography

Torsten Wiesel, in collaboration with David H. Hubel, provided fundamental insight into physiology of vision. Wiesel's work on charting the visual or striate cortex, the posterior section of the cerebral cortex, provided new insights into the complexity of the visual process that also proved to have direct clinical applications. Wiesel's discovery of critical periods in childhood development for learning to see led to earlier clinical intervention in visual problems in children. In 1981 Wiesel, along with Hubel and another brain researcher, Roger W. Sperry, shared the Nobel Prize in physiology or medicine.

Torsten Nils Wiesel was born on June 3, 1924, in Uppsala, Sweden, the son of Anna-Lisa Bentzer Wiesel and Fritz S. Wiesel, the chief psychiatrist at the Beckomberg Mental Hospital in Stockholm. Wiesel lived at his father's hospital as a youth, attending a private school where he was more interested in sports than academics. However, this attitude changed in 1941 when Wiesel entered medical school at the Karolinska Institute in Stockholm and studied neurophysiology under Carl Gustaf Bernhard. He also studied psychiatry during this time, and in 1954 he received his medical degree, becoming an instructor at the institute as well as an assistant in the Department of Child Psychiatry at Karolinska Hospital. Wiesel then came to the United States in 1955 to do postdoctoral work at the Wilmer Institute of Johns Hopkins School of Medicine in Baltimore, Maryland.

At Johns Hopkins, Wiesel worked under Stephen Kuffler, a researcher in visual physiology who had studied the nerve activity in the retina of the cat as well as in animals of other classes. Kuffler's exhaustive work had proved that the vision of mammals is distinctly different from that of non-mammals. Research with frogs had shown that their vision occurred in the optical nerve: that they had neurons, or nerve cells, sensitive not only to light and dark, but also to shapes, movements, and the boundaries between light and dark. Cats have no such specification in their ganglia, and lack the ability to give the detailed boundary information found in frogs. Yet, mammalian vision is stereoscopic, whereas non-mammalian appears to be in most cases binocular but lacking three dimensions. Wiesel became interested in the direction in which such investigations must logically lead: namely that the critical level of visual perception must take place in the brain of mammals. In 1958 David Hubel, a graduate of McGill University, returned to the institute from military service, and together Wiesel and Hubel set off on research that would result in a new theory of visual perception.

The striate or visual cortex is located at the back of the brain, an area of about 15 square centimeters in some of the monkeys Wiesel and Hubel would study. It had long been known, from accident victims, that this region of the cortex was involved with vision, and it is here that Wiesel and Hubel began their studies. They painstakingly measured electrical discharge of cells in the visual cortex with the aid of a microelectrode, a microscopic needle with an electrode built in to measure electrical impulses. Initially using anesthetized cats whose sight was trained on various patterns of light and dark, lines and circles, and probing the animal's visual cortex with their microelectrode at various angles, they discovered which cells in the cortex responded to which pattern or level of light. They also conducted experiments in which they injected the eyes of experimental animals with radioactively labeled amino acid. These amino acids would be taken up by the cell bodies of the retina and transported to cells in the visual cortex, giving a map of the pathway of vision. In some cases the laboratory animals were sacrificed and their visual cortexes dissected in order to see, by the use of autoradiographs or x-ray-like photos, where the labeled amino acids actually ended up. Such experiments, begun in 1959, used both cats and macaque monkeys. That same year Kuffler was appointed a professor at the Harvard University Medical School, and Wiesel and Hubel joined him there. Wiesel was appointed assistant professor of physiology, and became a full professor in 1964.

The Wiesel-Hubel team soon began publishing the results of their experimental method, and it was clear that they had uncovered new complexities to the visual process. Mapping the path of vision with radioactive amino acid, they showed that vision passed in coded signals from neuron to neuron through the optic nerve and split at the optic chiasm so that a representation of each half of the visual scene is projected deep in the brain on a nest of cells called the lateral geniculate nucleus, a way station to the cells in the cortex. From here, the path of vision continues to the back of the brain to various parts of the visual cortex, depending on the specialization of each cell. However, the pathway does not end there; indeed, the visual cortex was shown to be an early step in the processing of visual information. Information is sent back to parts of the brain from the cortex as well as back to the geniculate nuclei.

Within the visual cortex itself, Wiesel and Hubel made two important discoveries. First, they showed that there is a hierarchy of types of cells in the cortex, ranking from simple to complex to hypercomplex, depending on the information each is able to process. They termed the process of putting the millions of building blocks of visual information back together into a picture convergence. Various cells have preferences for the bits of visual information they process: size, shape, light, and sharpness of boundary differentiation, as well as which eye is sending the information. Such a complexity of visual processing destroys the old notion of sight being simply a film played in the mind. Instead, the accretion of bits of visual information into visual representation appears more similar to language processing than to an analogy of a film. Cells in the visual cortex "read" neuron messages. Their second major discovery was a further organization of the cortical cells into roughly vertical divisions of two types: orientation columns and ocular dominance columns. The orientation columns transform what is essentially circular information from the retina and geniculate nerve cells into linear information, while the ocular combine the neural information from both eyes to provide three-dimensional vision. Within these columns are simple, complex, and hypercomplex cells working toward a progressive convergence of visualization. Until the time of Wiesel's and Hubel's work, it was assumed that all cells of the cerebral cortex were more or less uniform. Wiesel and Hubel showed that the visual cortex is constituted of a cell pattern, which appears to be designed specifically for vision. As a result of their discovery, current theory now posits that the rest of the cerebral cortex may follow this form-follows-function rule.

Wiesel and Hubel researched another experimental model in which they used kittens to study the effect of various visual impairments on development. They discovered that if one eye were deprived of visual stimuli during the third to fifth postnatal weeks, the central functioning of that eye would always be suppressed from cortical processing. Kittens, and by extension mammals in general, though born with a complete visual cortex, must still "learn" to see. Even if an early impairment is later corrected, the repaired eye will remain functionally impaired as far as the visual cortex is concerned. The realization that there is a critical stage for visual development revolutionized the field of pediatric ophthalmology, calling for the earliest possible intervention in cases of strabismus, or crossed eyes, and congenital cataracts.

By 1973, Wiesel succeeded Kuffler as chair of the Department of Neurobiology at Harvard, and was named the Robert Winthrop Professor of Neurobiology in 1974. Wiesel became a naturalized U.S. citizen in 1990. Wiesel has been the recipient of many awards over the years, including the Lewis S. Rosentiel Award in 1972, the Jonas S. Friedenwald Memorial Award in 1975, the Karl Spencer Lashley Prize in 1977, the Louisa Gross Horowitz Prize in 1978, and the George Ledlie Prize in 1980. Wiesel shared a 1981 Nobel Prize, with Hubel and Sperry (who worked at California Institute of Technology). The Karolinska Institute in Stockholm, which administers the prize and where Wiesel began his professional career, praised Hubel and Wiesel for their discoveries concerning information processing in the visual system. Wiesel and Hubel continued their close working relationship until Wiesel left Harvard in 1984 to head the neurobiology lab at Rockefeller University where he continued his researches on vision. In 1992 he was named president of Rockefeller University.