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 Beckomberga Mental Hospital in Stockholm. Wiesel entered medical school at the Karolinska Institute in Stockholm in 1941 and studied neurophysiology and psychiatry. 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.

At Johns Hopkins, Wiesel worked under Stephen Kuffler, whose exhaustive work had proved that the vision of mammals is distinctly different from that of non-mammals. Wiesel became interested in the idea that the critical level of visual perception must take place in the brain of mammals. In 1958, Wiesel set off with David Hubel on...