Wiesel, Torsten Nils (1924-), a Swedish-born American neurobiologist, made important discoveries about how the brain processes visual information. For this groundbreaking work, he shared the 1981 Nobel Prize in physiology or medicine with American physician David Hunter Hubel and American biologist Roger Wolcott Sperry .

In 1958, Wiesel and Hubel were colleagues at the Johns Hopkins laboratory. The two began investigating the visual cortex, the part of the brain responsible for processing visual input. They found that the visual cortex includes a system of specialized nerve cells that processes the many small pieces of visual information perceived by the retina into one large image. Wiesel and Hubel also discovered that the nerve cells are organized into columnlike structures. In later studies, the pair showed the importance of early visual development. As a result, ophthalmologists now correct childhood eye problems, such as crossed eyes, as early as possible.

Wiesel entered medical school at the Karolinska Institute in Stockholm in 1941. While there, he studied neurophysiology and psychiatry. He received his medical degree in 1954, and in 1955 he became a postdoctoral fellow at the Wilmer Institute of Johns Hopkins School of Medicine in Baltimore. It was during this time that Wiesel met Hubel, and the two scientists began a collaboration that lasted over 20 years.

In 1959, Wiesel and Hubel both left Hopkins for Harvard University, where Wiesel was appointed assistant professor of physiology, becoming a full professor in 1964. He became chairman of the department of neurobiology in 1973. Ten years later, Wiesel joined the faculty at Rockefeller University as a professor of neurobiology. In 1992, he was named president of the university.