Thursday, October 31, 2013

The Most Studied Amnesic Patient (H.M ) And His Impact to Neuroscience

Maria K. Almoite

Today’s prevailing understanding of memory derived from examining the origin of memory disorders. A well-known cognitive disorder circumscribed by memory impairments is known as Amnesia. It is a condition in which memory (LTM) is lost beyond the natural onset of forgetting (i.e. loss of retention). Amnesia can be classified into two: Retrograde (loss of information before amnesia) and Anterograde (inability to learn new information). The purpose of this analysis is to explore the most-famous case of Anterograde Amnesia and the revolutionary contribution of H.M. to the field of neuroscience.

          The case of H.M was first heard by Scoville and Millner (1953) in a newspaper. H.M. suffered from anterograde amnesia since 1953, as a result of an experimental surgery of MTL structures to relieve his severe epileptic seizures (Scoville, 1954, 1968; Scoville et al., 1953; Scoville & Milner, 1957).  Scoville and Millner (1957) conducted series of tasks to explore his pre and post knowledge prior the onset of his Amnesia. Consequently, Milner administered performance tasks and discovered that H.M. was able to learn simple sensorimotor skills despite of his pervasive amnesia. (e.g. tracing a simple diagram improved with practice). Scoville and Milner (1957) then concluded that H.M.’s semantic memory (e.g. general knowledge/daily life) was not impaired, but he was unable to develop new declarative (e.g. episodic/factual) memories. The researchers concluded that the anterior hippocampus and hippocampal gyrus (separate or together) are concerned in the retention of experience (Scoville and Milner, 1957).

The New York Times published “H. M., an Unforgettable Amnesiac, Dies at 82” a piece solely devoted to H.M., and his huge contribution the field of memory research. Dr. Milner, a cognitive neuroscientist who worked very closely to H.M. reminisced about H.M.’s patience and his willingness to do experimental tasks his given. Therefore, H.M.’s brain preserved for future study, in the same spirit that Einstein’s was, as an irreplaceable artifact of scientific history.

Indeed, Anterograde Amnesia also relates back to the synaptic consolidation process in which neurons in the hypothalamus make connections with the thalamus, which in turn makes connections with the cortex of the brain (i.e. where long-term memories are stored). Hence, damage in anterograde amnesia impairs the encoding process of LTM store.
Remarkably, this analysis largely differs than any other theories found. H.M. indeed is one of the most-studied amnesic patients, who allowed us to expand our overall understanding of the function and purpose of our memory. The articles allowed us to understand the case of H.M in a deeper level by proving detailed information (e.g. statistical and procedures). Simply, Understanding the basis of human memory, its capacity formation, and it’s applicability to the real world can help shape our overall understanding of interacting fields in today’s society.   

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