Famous subject H.M. dies at age 82

Henry G. Molaison, 82, of Windsor Locks, CT died on Tuesday. He is known in the medical and scientific literatures as “the amnesic patient, H.M.” He was born in Manchester, CT and graduated from East Hartford High School. In 1953, he underwent an experimental brain operation at the Hartford Hospital to relieve his seizure disorder. Immediately after the operation, Mr. Molaison showed a profound amnesia, which became the topic of intense scientific study for more than five decades. From age 27 on, he was unable to establish new memories for events in his everyday life and to acquire general information about the world in which he lived. His memory impairment was “pure” and not accompanied by intellectual or personality disorders. For this reason, and because the operation has not been repeated, he is the most widely studied and famous case in the neuroscience literature of the 20th and 21st centuries. Mr. Molaison’s contributions to knowledge about memory have been groundbreaking, and researchers worldwide are in his debt. Burial will be private.

Brief History of HM (from Wikipedia):

HM suffered from intractable epilepsy that has been often—though inconclusively—attributed to a bicycle accident at the age of nine. He suffered from partial seizures for many years, and then several tonic-clonic seizures following his sixteenth birthday. In 1953, HM was referred to William Scoville, a surgeon at Hartford Hospital, for treatment.

Scoville localized HM's epilepsy to his left and right medial temporal lobes (MTLs) and suggested surgical resection of the MTLs as a treatment. On September 1, 1953, Scoville removed parts of HM's MTL on both sides of his brain. HM lost approximately two-thirds of his hippocampus, parahippocampal gyrus, and amygdala. His hippocampus appears entirely nonfunctional because the remaining 2 cm of hippocampal tissue appears atrophic and because the entire entorhinal cortex, which forms the major sensory input to the hippocampus, was destroyed. Some of his anterolateral temporal cortex was also destroyed.

After the surgery he suffered from severe anterograde amnesia: although his working memory and procedural memory were intact, he could not commit new events to long-term memory. According to some scientists (e.g., Schmolck, Kensinger, Corkin, & Squire, 2002), HM is impaired in his ability to form new semantic knowledge but researchers argue over the extent of this impairment. He also suffered moderate retrograde amnesia, and could not remember most events in the 3–4 -day period before surgery, and some events up to 11 years before, meaning that his amnesia was temporally graded. However, his ability to form long-term procedural memories was still intact; thus he could, as an example, learn new motor skills, despite not being able to remember learning them.

The case was first reported in a paper by Scoville and Brenda Milner in 1957.