Henry Molaison (HM) was famous in neuroscience for the study of knowledge he provided about memory impairment and amnesia. He was not a neuroscientist but a patient who contributed in the study of learning mechanism and memory formation. It was thought that his exact brain surgery allowed a good understanding of how particular areas of brain may be linked to learning process and memory formation. The process of managing memory in brain mechanism was hypothesized previously but it was not verified by the findings of Molaison’s memory loss and learning disabilities. In this way, his case was taken to provide information about brain pathology and helped to form the theories of normal memory function.
Henry Gustav Molaison (February 26, 1926 – December 2, 2008) was widely known as HM in the study of behavioral neuroscience. He was an American memory disorder patient who had a bilateral medial temporal lobectomy. The anterior two thirds of his hippocampus, parahippocampal cortices, entorhinal cortices, piriform cortices and amygdalae were surgically resected in an attempt to cure the seizures of his epilepsy. He was widely studied from late 1957 until his death in 2008. His case played an important role in the development of theories that explain the link between brain function and memory formation. Cognitive neuropsychology is a branch of psychology that aims to understand how the structure and function of human brain relate to specific psychological processes. He resided in a care institute in Windsor Locks, Connecticut, where he was the subject of ongoing investigation to develop the modern theories of cognitive science.
The imaging of Molaison’s brain in the late 1990s revealed that the extent of damage was more widespread than previous theories had accounted for anterograde and retrograde amnesia. It was making very hard to identify any one particular region or even isolated set of regions that were responsible for his deficits and inability. The study of Molaison’s living and working revolutionized understanding for the organization of human memory and working mechanism. It has provided broad evidence for the rejection of old theories and the formation of new theories on human memory and learning spectrum. The major insights of modern theory were outlined for learning mechanism and memory formation, in particular about its processes and underlying neural structures (Kolb & Whishaw 1996).
After the death of Henry Molaison, his brain was fixed and preserved for further study. On December 4, 2009, Annese’s group acquired 2401 brain slices with only two damaged slices and 16 potentially problematic slices. The digital 3D reconstruction of his brain was finished at the beginning of 2014. It opened the new frontier of neuroscience which could help in finding the facts of learning mechanism and the memory formation of human brain. Results of the pathological study were published in Nature Communications for January 2014. It was a great surprise, the researchers found that the half of Molaison’s hippocampus had survived the 1953 brain surgery.
The remaining part of hippocampus had deep implications on past and future interpretations of Molaison’s neuro-behavioral profile. The previous literature of findings was not true which described Henry Molaison as a pure hippocampus lesion patient. Molaison’s brain was the subject of an unprecedented anatomical study funded by the Dana Foundation and the National Science Foundation. The project of Brain Observatory at UC San Diego headed by Jacopo Annese provided a complete microscopic survey of entire brain. It has revealed the neurological basis of Molaison’s historical memory impairment at cellular resolution.