The ability to recall accurately vast amounts of autobiographical information spanning most of a lifetime, without the use of practiced mnemonics, is very rare. Only a handful of people have been identified so far. Testing of these individuals has shown that there is better recall of public and personal autobiographical events as well as the days and dates on which these events occurred. However, performance on other standard memory tests is generally average. For superior autobiographical memory, nine brain structures were identified as being different from controls. These included differences in the inferior and middle temporal gyri and temporal pole (BA 20, 21 and 38, respectively), the anterior insula, and the parahippocampal gyrus, (BA 36).
The right temporal pole (BA 21,BA 38) and medial temporal gyrus (BA 21) in addition to the parahippocampus and right anterior insula have been shown, using positron emission tomography, to be primarily engaged during affect-laden autobiographical memory ecphory (cued recovery of a past event eliciting an imagined image or representation of the information). This parallels the extensive memory database of tested subjects, which seemingly retains a high number of retrieval cues stimulating the recollection of vivid and often emotional memories.
The report also discussed the possibility of common underlying mechanisms with obsessive compulsive disorder. Findings of morphological differences in the anterior putamen, caudate and posterior pallidum and behavioral trends towards obsessive tendencies were consistent with this line of thought. Intentional rehearsal and review of autobiographical memories was recorded for most subjects under study but did not appear to be the sole means by which the subjects achieved their rich repertoire of memories. Instead, subjects appeared to have some inherent ability to retain and retrieve vast amounts of public and autobiographical events, well beyond what one may expect from simple rehearsal. Highly superior autobiographical memory was specific to the domain of recalling events that were autobiographical in nature, as opposed to having strong memory generally.
The authors suggest that the structural changes found in the highly superior autobiographical memory population may contribute to the more efficient use of the same “hardware.” It is currently not known whether the anatomical differences are the cause or result of superior autographical memory performance. More research is needed in this area.
LePort AKR, Mattfeld AT, Dickinson-Anson H, Fallon JH, Stark CEL, Kruggel F, Cahill L, McGaugh JL: Behavioral and neuroanatomical investigation of highly superior autobiographical memory (HSAM). Neurobiology of Learning and Memory 98(1): 78-92 (2012).
