The Missing Hippocampus
14 min readIn 1953, a twenty-seven-year-old man named Henry Molaison underwent surgery to treat severe epilepsy. Surgeons removed most of his hippocampus, a small curved structure deep in the temporal lobe, from both hemispheres. The seizures improved. Henry stopped making long-term memories.
Henry could carry on a perfectly coherent conversation. His intelligence was intact. His working memory functioned normally. He could hold information in mind, reason about it, and respond appropriately. He had full access to memories formed before the surgery. His personality was unchanged.
He just couldn’t form new long-term memories. Every conversation started fresh. His doctors reintroduced themselves at every visit for the next fifty-five years. He could read the same magazine and find it novel each time. He would grieve his uncle’s death anew every time someone told him.