The science of memory

THE two-letter initials H.M. are the most famous in the history of the brain sciences. Henry Gustav Molaison was a mechanic in Connecticut and suffered from chronic epilepsy since his childhood. In 1953, a neurosurgeon removed a tiny portion of his midbrain, known as the hippocampal region. This cured Henry’s debilitating illness but had a tragic side-effect. Henry could no longer create new memories; every time he met someone or experienced something, it was as if for the first time. For all purposes, Henry was living permanently in the present.

However, Henry’s botched surgery revolutionized brain research—until then, it was believed that memory functions depended on the entire brain. No one knew the centrality of the hippocampal region as the engine of memory formation and for renewing old memories. For over half a century, Henry willingly subjected himself to numerous researches and was known worldwide as H.M. to protect his identity. His real name was revealed only after his death in 2008.