A life of splits

Abstract

The idea of splitting the brain has long been of interest as a test of Cartesian dualism: would separating the two sides of the brain create separate minds, or would the mind somehow remain unified? The German psychologist Gustav Fechner was one who contemplated this question, and the British psychologist William McDougall even tried to persuade the physiologist Charles Sherrington to cut his, McDougall’s, corpus callosum, thereby splitting his brain, if he were to become incurably ill. As a dualist, he was no doubt convinced that his mind would remain unified. Fortunately for McDougall, but perhaps unfortunately for science, he never underwent the operation. In the early 1940s William van Wagenen, a neurosurgeon at the University of Rochester Medical Center in Rochester, NY, elected to section the corpus callosum in a number of patients in the hope of relieving their intractable epilepsy. The operation proved surprisingly successful, and psychological investigations seemed to show little or no mental effect of the operation. It seemed then that the dualists were right, or perhaps the corpus callosum was simply of no relevance to mental function—the neurologist who undertook the psychological testing jocularly suggested that the role of the corpus callosum was to keep the cerebral hemispheres from sagging. The picture was to change dramatically, though, in the 1960s, when two Los Angeles neurosurgeons, Philip Vogel and Joseph Bogen, operated on another series of patients with intractable epilepsy, and were again largely successful in alleviating their seizures. This time, though, careful psychological testing revealed that the mind was indeed split in remarkable ways. As an undergraduate at Dartmouth College in Hanover, New Hampshire, Michael Gazzaniga had learned of split-brain research on cats and monkeys, carried out by Roger Sperry and associates at the California Institute of Technology (Caltech), and became interested in further testing …