In the 1940s, Wilder Penfield carried out a series of experimental psychosurgeries with the psychiatrist D. Ewen Cameron. This article explores Penfield's brief foray into psychosurgery and uses this episode to re-examine the emergence of his surgical enterprise. Penfield's greatest achievement - the surgical treatment of epilepsy - grew from the same roots as psychosurgery, and the histories of these treatments overlap in surprising ways. Within the contexts of Rockefeller-funded neuropsychiatry and Adolf Meyer's psychobiology, Penfield's frontal lobe operations (including a key operation on his sister) played a crucial role in the development of lobotomy in the 1930s. The combination of ambiguous data and the desire to collaborate with a psychiatrist encouraged Penfield to try to develop a superior operation. However, unlike his collaboration with psychiatrists, Penfield's productive working relationship with psychologists encouraged him to abandon the experimental "gyrectomy" procedure. The story of Penfield's attempt to find a better lobotomy can help us to examine different forms of interdisciplinarity within biomedicine.