The scientific legacy of HM’s missing memories

The latest edition of Neuron has a fantastic tribute to the recently departed amnesic Patient HM, “probably the best known single patient in the history of neuroscience”, covering the scientific work he participated in and what it has told us about the structure of memory.

The piece is by respected memory researcher Larry Squire and he tackles HM’s personal history while also reviewing his contributions to science through numerous landmark studies.

It can be said that the early descriptions of H.M. inaugurated the modern era of memory research. Before H.M., due particularly to the influence of Karl Lashley, memory functions were thought to be widely distributed in the cortex and to be integrated with intellectual and perceptual functions.

The findings from H.M. established the fundamental principle that memory is a distinct cerebral function, separable from other perceptual and cognitive abilities, and identified the medial aspect of the temporal lobe as important for memory.

The implication was that the brain has to some extent separated its perceptual and intellectual functions from its capacity to lay down in memory the records that ordinarily result from engaging in perceptual and intellectual work.

The article is fascinating not least because it dispels a few common myths about HM – such as the original study showed the hippocampus was necessary for memory when HM also had the amygdala and parahippocampal gyrus removed and so it wasn’t possible to say which were most important.

It also notes that the original studies over-stated how much brain was removed owing to the basic knowledge of neuroanatomy that existed at the time.

Link to ‘The Legacy of Patient H.M. for Neuroscience’.
Link to PubMed entry for same.

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