Henry Molaison

Henry Gustav Molaison, known widely as H.M., was an American epileptic man who in 1953 received a bilateral medial temporal lobectomy to surgically resect parts of his brain—the anterior two thirds of his hippocampi, parahippocampal cortices, entorhinal cortices, piriform cortices, and amygdalae—in an attempt to cure his epilepsy. Although the surgery was partially successful in controlling his epilepsy, a severe side effect was that he became unable to form new memories.