Psychical Discharges (Cortical Stimulation)

1941

Wilder Penfield (1891–1976)

A young psychologist is under a surgical tent at the Montreal Neurological Institute. It is 1939, and psychologist Molly Harrower is about to record some of the most interesting data ever provided by brain surgery patients. Her role is to record verbatim what each one reports. The patients all suffer from epilepsy and have agreed to participate in an innovative procedure devised by neurosurgeon Wilder Penfield. With patients under local anesthetic, Penfield surgically exposed the cortex of the brain; then, using a tiny electrode, he stimulated various parts of the brain. Some spots appeared to be related to the aura that many epileptic patients experience prior to a seizure; these he surgically removed. Areas relevant to movement and sensation yielded the expected experiences when stimulated; for example, patients reported seeing flashes of color when the visual cortex was touched.

When Penfield first reported these findings in 1941, he also indicated that further stimulation of the temporal lobe produced surprising results, including what he called “experiential hallucinations,” or psychical discharges. When certain areas in the temporal lobe were touched by the electrode, patients reported hearing songs they had last heard as a child, or they saw a portrayal of some event they may have viewed in a movie. In one famous reenactment, the patient cried out, “I can smell burned toast” when a seizure origin point was stimulated. Penfield thought these hallucinations were accurate flashbacks of the original experience. He also found what he termed “interpretative illusions,” which included experiences of déjà vu and perceptual distortions as well as a sense of unreality, euphoria, or dread.

Most of his patients reported these experiences as quite intense, with qualities very different from everyday experiences—more dreamlike than the reality of daily life. Penfield’s intention was to help his patients gain relief through surgical intervention. But he found that cortical stimulation also had implications for Localization of Brain Function and for memory.

SEE ALSO Localization of Brain Function (1861), Brain Imaging (1924), Split-Brain Studies (1962)

Dr. Wilder Penfield (left) and Dr. Maitland Baldwin. Penfield, one of the leading neurologists of his era, demonstrated how electrically stimulating the temporal lobe could yield psychical discharges, in which patients respond by describing flashbacks and déjà vu experiences.