The Legacy of Patient H.M. for Neuroscience

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• H.M. had a remarkable capacity for sustained attention, including the ability to retain information for a period of time after it was presented.

• H.M. not only motivated the development of an animal model of human memory impairment and the subsequent delineation of the medial temporal lobe memory system

• This demonstration provided the first hint that there was more than one kind of memory in the brain and suggested that some kinds of memory (motor skills) must lie outside the province of the medial temporal lobe

• H.M. is probably the best known single patient in the history of neuroscience.

• severe memory impairment, which resulted from experimental neurosurgery to control seizures

• in 1953 at the age of 27 he had become so incapacitated by his seizures

• Scoville offered H.M. an experimental procedure that he had carried out previously in psychotic patients,

• was someone who forgot daily events nearly as fast as they occurred

• underestimated his own age, apologized for forgetting the names of persons to whom he had just been introduced

• publication became one of the most cited papers in neuroscience (nearly 2500 citations) and is still cited with high frequency.

• It can be said that the early descriptions of H.M. inaugurated the modern era of memory research

• The findings from H.M. established the fundamental principle that memory is a distinct cerebral function

• structures within H.M.’s large lesion were important for understanding his impairment and, more broadly, what structures are important for memory

• the study of H.M. also led to fundamental insights into the function of the medial temporal lobe and the larger matter of how memory is organized in the brain.

• Yet when his attention was diverted to a new topic, he forgot the whole event.

• material was not easy to rehearse (in the case of nonverbal stimuli like faces or designs), information slipped away in less than a minute

• These findings supported a fundamental distinction between immediate memory and long-term memory

• This important finding implied that the medial temporal lobe is not the ultimate storage site for previously acquired knowledge

• identification of the multiple memory systems of the mammalian brain.

• The early paper is sometimes cited incorrectly as evidence that the hippocampus is important for memory, but this particular point could not of course be established from a lesion that, by the surgeon’s description, included the hippocampus, amygdala, and the adjacent parahippocampal gyrus. As Milner subsequently wrote, “Despite the use of the word ‘hippocampal’ in the titles of my papers with Scoville and Penfield, I have never claimed that the memory loss was solely attributable to the hippocampal lesions” (Milner, 1998). Indeed, the original paper ends, quite appropriately, with the statement: