Initial characterization

Parker ES, Cahill L, McGaugh JL (2006). A case of unusual autobiographical remembering. Neurocase, 12(1):35-49.

This report describes AJ, a woman whose remembering dominates her life. Her memory is “nonstop, uncontrollable, and automatic.” AJ spends an excessive amount of time recalling her personal past with considerable accuracy and reliability. If given a date, she can tell you what she was doing and what day of the week it fell on. She differs from other cases of superior memory who use practiced mnemonics to remember vast amounts of personally irrelevant information. The investigators proposed the name hyperthymestic syndrome, from the Greek word thymesis meaning remembering, and that AJ is the first reported case.

First group study and preliminary MRI findings

LePort, AKR, Mattfeld, AT, Dickinson-Anson, H, Fallon JH, Stark, CEL, Kruggel, FR, Cahill, L, & McGaugh, JL (2012) Behavioral and neuroanatomical investigation of Highly Superior Autobiographical Memory (HSAM). Neurobiology of Learning and Memory, 98(1), 78-92.

The study reports findings based on eleven participants expressing HSAM. Participants were identified and subsequently characterized based on screening for memory of public events. They were then tested for personal autobiographical memories and for memory assessed by laboratory memory tests. Additionally, whole-brain structural MRI scans were obtained. Results indicated that HSAM participants performed significantly better at recalling public and personal autobiographical events as well as the days and dates on which these events occurred. However, their performance was comparable to age- and sex-matched controls on most standard laboratory memory tests. Neuroanatomical results identified several structures as being morphologically different from those of control participants.

Evidence of false memories in HSAM

Patihis L, Frenda SJ, LePort AKR, Petersen N, Nichols RM, Stark CEL, McGaugh JL, & Loftus EF (2013). False memories in highly superior autobiographical memory individuals. Proceedings of the National Academy of Sciences, 110(52): 20947-20952.

The recent identification of HSAM raised the possibility that there may be individuals who are immune to memory distortions. The investigators measured HSAM participants’ and age- and sex-matched controls’ susceptibility to false memories using several research paradigms. HSAM participants and controls were both susceptible to false recognition of nonpresented critical lure words in an associative word-list task. In a misinformation task, HSAM participants showed higher overall false memory compared with that of controls for details in a photographic slideshow. HSAM participants were equally if not more likely than controls to mistakenly report they had seen nonexistent footage of a plane crash. Finding false memories in a superior–memory group suggests that malleable mechanisms may be fundamental to this type of  remembering.

Forgetting rates in HSAM

LePort AKR, Stark SM, McGaugh JL, & Stark CEL (2016) Highly Superior Autobiographical Memory: Quality and quantity of retention over time. Frontiers in Psychology, 6:2017.

The investigators examined the differences in memory for HSAMs and controls for very recent information as well as more remote memories. Interestingly, for memories that were one-week old, both HSAMs and controls recalled the same amount of information, though the quality of their memories differed. However, at a longer delay of one-month, HSAMs displayed much greater recall performance than controls. Specifically, HSAMs showed remarkable consistency for memories that were one-week and one-month old, while controls’ recall declined dramatically after one month. Finally, they showed that the degree of consistency of recall was correlated with obsessive-compulsive tendencies in the HSAM group

No advantage in other tests of memory identified in HSAM

LePort AKR, Stark SM, McGaugh JL, & Stark CEL (2017).  A cognitive assessment of Highly Superior Autobiographical Memory.  Memory. In press.

The investigators examined whether enhanced abilities in the domains of verbal fluency, attention/inhibition, executive functioning, mnemonic discrimination, perception, visual working memory, or the processing of and memory for emotional details might contribute critically to HSAM. The results suggest that superior cognitive functioning is an unlikely basis of HSAM, as only modest advantages were found in only a few tests. In addition, the investigators examined HSAM subjects’ memory of the testing episodes. Interestingly, HSAM participants recalled details of their own experiences far better than those experiences that the experimenter shared with them. These findings provide additional evidence that HSAM involves, relatively selectively, recollection of personal, autobiographical material.