In 1939, a group of 10 people between the ages of 10 and 43, all with epilepsy, traveled to the University of Rochester Medical Center, where they would become the first people to undergo a radical new surgery.
The patients were there because they all struggled with violent and uncontrollable seizures. The procedure they were about to have was untested on humans, but they were desperate—none of the standard drug therapies for seizures had worked.
Between February and May of 1939, their surgeon William Van Wagenen, Rochester’s chief of neurosurgery, opened up each patient’s skull and cut through the corpus callosum, the part of the brain that connects the left hemisphere to the right and is responsible for the transfer of information between them. It was a dramatic move: By slicing through the bundle of neurons connecting the two hemispheres, Van Wagenen was cutting the left half of the brain away from the right, halting all communication between the two.
When Michael Gazzaniga first learned about the Rochester patients as an undergraduate research intern in 1960, he was curious—and skeptical. Gazzaniga’s timing was fortuitous: Roger Sperry, who headed the neuroscience lab where Gazzaniga worked at the California Institute of Technology, had begun split-brain research on cats and monkeys just a few years earlier. Sperry found that severing the corpus callosum of those animals had affected their behavior and cognitive functioning.
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