Henry Molaison - Biography

Biography

Henry Molaison was born on February 26, 1926 and suffered from intractable epilepsy that has sometimes been attributed to a bicycle accident at the age of seven. This accident was initially reported to have occurred at age nine, but was corrected by the patient's mother at a later stage. He suffered from partial seizures for many years, and then several tonic-clonic seizures following his sixteenth birthday. In 1953 he was referred to William Beecher Scoville, a neurosurgeon at Hartford Hospital, for treatment.

Scoville localized Molaison'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, Molaison's bilateral medial temporal lobe resection included the hippocampal formation and adjacent structures including most of the amygdaloid complex and entorhinal cortex was removed. His hippocampus appeared entirely nonfunctional because the remaining 2 cm of hippocampal tissue appeared 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—which was successful in its primary goal of controlling his epilepsy—he suffered from severe anterograde amnesia: although his working memory and procedural memory were intact, he could not commit new events to his explicit memory. According to some scientists, Molaison was 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 1–2-year period before surgery, nor some events up to 11 years before, meaning that his amnesia was temporally graded. However, his ability to form long-term procedural memories was intact; thus he could, for 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. Near the end of his life, Molaison regularly filled in crossword puzzles. He was able to fill in answers to clues that referred to pre-1953 knowledge. For post-1953 information he was able to modify old memories with new information. For instance, he could add a memory about Jonas Salk by modifying his memory of polio.

He died on December 2, 2008.