Stimulated Mental States

During the 1940s and early 1950s, a Canadian doctor explored "psychic effects" of stimulation during brain operations on humans. Wilder Penfield was a highly respected and specialized brain surgeon at the Montreal Neuropsychiatric Institute. Hundreds of patients came to him specifically for brain surgery to relieve epilepsy.

Why was it significant that Penfield's patents had epilepsy?

Epilepsy is a word that describes a symptom—seizures—rather than a disease. . Seizures can be caused by many things. Brain surgery is not usually needed to cure epilepsy, but in some cases when a distinct, damaged area of the brain causes seizures, surgery may help. The fact that Penfield's patients were epileptic proved to be important to his research, because later studies showed that only epileptic patients typically responded to direct brain stimulation by having experiences they could report to a doctor.

What did Penfield do during surgery?

During surgery, Penfield allowed his patients to regain consciousness so they could say whether they felt anything when a weak electrical current stimulated their exposed brains. If they did, it would indicate that the brain tissue at that location was still alive and functioning and should not be removed. The brain has no pain receptors itself, so the patient did not feel any pain from the electrical stimulation. Penfield put little numbered pieces of paper on the surface of the cortex to indicate where he had stimulated with electricity.

Sometimes stimulation produced vivid constructions that resembled memories. Here is one example:

A young man, J.T.,...who had recently come from his home in South Africa, cried out when the superior surface of his right temporal lobe was being stimulated: "Yes, Doctor! Yes, Doctor! Now I hear people laughing-my friends-in South Africa." After stimulation was over, he could discuss his...astonishment, for it had seemed to him that he was with his cousins at home where he and the two young ladies were laughing together. (Penfield, 1962)


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Copyright © 2007 Russ Dewey