Wilder Graves Penfield OM CC CMG FRS (January 26, 1891 – April 5, 1976) was an American-Canadian neurosurgeon. He expanded brain surgery's methods and techniques, including mapping the functions of various regions of the brain such as the cortical homunculus. His scientific contributions on neural stimulation expand across a variety of topics including hallucinations, illusions, and déjà vu. Penfield devoted much of his thinking to mental processes, including contemplation of whether there was any scientific basis for the existence of the human soul.