Canadian neurosurgeon Wilder Penfield performed pioneering experiments in the 1940s and 1950s. During extensive brain surgeries, he applied electrodes to different regions of the brain and stimulated them. He then asked patients what they felt. He recorded and correlated sensations, images, even memories, as reported by the patients. By this means he mapped the brain and found, for example, that the brain area involved with lips and fingers occupies as much space as the area which handles the entire trunk of the body.
