A surgeon mapped the brain by touching it while patients were awake and talking

To locate epilepsy-causing tissue without damaging healthy brain, Wilder Penfield electrically stimulated the exposed cortex of conscious patients and asked what they felt. Recording which touch made a patient report a twitch in their thumb or lip let him build the first map of the brain's body surface — the sensory 'homunculus'.

— Wilder Penfield & Theodore Rasmussen, The Cerebral Cortex of Man — Macmillan, 1950
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