Patient HM

Henry Molaison, commonly known as “Patient H.M.” was a man who underwent a bilateral medial temporal lobectomy to treat violent seizures. After this surgery, he had severe anterograde amnesia and some retrograde amnesia. The medial temporal lobe became known as the hippocampus, and we learned from Patient H.M. that is is important in encoding declarative memories, but not procedural memories. The hippocampus is also important for storing spatial memories, and place cells are known to fire both when rats are at a specific location, and during sleep so these spatial memories can be consolidated.