Henry Molaison

Henry Gustav Molaison (February 26, 1926 – December 2, 2008), 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. His unique case also helped define ethical standards in neurological research, emphasizing the need for patient consent and the consideration of long-term impacts of medical interventions. Furthermore, Molaison's life after his surgery highlighted the challenges and adaptations required for living with significant memory impairments, serving as an important case study for healthcare professionals and caregivers dealing with similar conditions.

A childhood bicycle accident is often advanced as the likely cause of H.M.'s epilepsy. H.M. began to have minor seizures at age 10; from 16 years of age, the seizures became major. Despite high doses of anticonvulsant medication, H.M.'s seizures were incapacitating. When he was 27, H.M. was offered an experimental procedure by neurosurgeon William Beecher Scoville. Previously, Scoville had only ever performed the surgery on psychotic patients.

H.M. was extensively studied from late 1957 until his death in 2008. He resided in a care institute in Windsor Locks, Connecticut, where he was the subject of ongoing investigations. His case played an important role in the development of theories that explain the link between brain function and memory, and in the development of cognitive neuropsychology, a branch of psychology that aims to understand how the structure and function of the brain relates to specific psychological processes.

Molaison's brain was kept at University of California, San Diego, where it was sliced into histological sections on December 4, 2009. It was later moved to the MIND Institute at UC Davis. The brain atlas constructed from him was made publicly available in 2014.

Henry Molaison was born on February 26, 1926, in Manchester, Connecticut, United States, and experienced intractable epilepsy that has sometimes been attributed to a bicycle accident at the age of seven, in which he was knocked out by a man riding a bicycle while playing on a local street, causing him to lose consciousness and pass out for around five minutes and suffer from minor convulsions shortly afterwards. He had minor or partial seizures for many years, and then major or tonic-clonic seizures following his 16th birthday. He worked for a time on an assembly line but, by the age of 27, he had become so incapacitated by his seizures, despite high doses of anticonvulsant medication, that he could not work nor lead a normal life.

In 1953, Molaison was referred to William Beecher Scoville, a neurosurgeon at Hartford Hospital. Scoville localized his epilepsy to the left and right medial temporal lobes (MTLs) and suggested their surgical resection. On September 1, 1953, Scoville removed Molaison's medial temporal lobes on both hemispheres including the hippocampi and most of the amygdalae and entorhinal cortex, the major sensory input to the hippocampi. His hippocampi appeared entirely nonfunctional because the remaining 2 cm of hippocampal tissue appeared to have atrophied and some of his anterolateral temporal cortex was also destroyed.

The hippocampi play an extremely important role in the brain for forming and remembering memories, and for having a long-term memory span, but in 1953 (when Molaison had the surgery) this was not known to doctors, surgeons, and scientists, as knowledge and studies of the brain was considerably less advanced back then.

After the surgery, which was partially successful in controlling his seizures, Molaison developed severe anterograde amnesia: although his working memory and procedural memory were intact, because his hippocampi was severed from the rest of his brain, Molaison lost his ability to remember and his memory was lost almost entirely, leading him to have an extremely severe memory disorder. Because he lost his memory and would easily forget things he just learned, and often had the memory span of only around 30 seconds, Molaison easily forgot events that he experienced, people whom he saw, and actions he undertook, leading him to have a very difficult life and being extremely forgetful, which he struggled to cope with and adjust to properly.