Hyperthymesia

Abstract: Highly superior autobiographical memory (HSAM) is a recently identified ability that has been difficult to explain with existing memory science. The present study measured HSAM participants’ and age/gender-matched controls’ on a number of behavioural measures to test three main hypotheses: imaginative absorption, emotional arousal, and sleep. HSAM participants were significantly higher than controls on the dispositions absorption and fantasy proneness. These two dispositions also were associated with a measure of HSAM ability within the hyperthymesia participants. The emotional-arousal hypothesis yielded only weak support. The sleep hypothesis was not supported in terms of quantity, but sleep quality may be a small factor worthy of further research. Other individual differences are also documented using a predominantly exploratory analysis. Speculative pathways describing how the tendencies to absorb and fantasise could lead to enhanced autobiographical memory are discussed.

Abstract: Solomon Veniaminovich Shereshevskii (1886-1958) was a man studied by psychologist Aleksandr Romanovich Luria, who thought that Shereshevskii’s (S) remarkable memory caused a psychological syndrome with cognitive deficits; consequently, Luria not only described S’s memory, but also other aspects of his life such as his synaesthesia, mental imagery, preferences, strengths, weaknesses and personality [1]. Likewise, more recently the phrase “hyperthymestic syndrome” (hyperthymesia) has been coined in order to de‐ scribe the case of a woman (AJ) whose autobiographical memory is extraordinary, but she has said “it is a burden” [2]. On the other hand, Kanner’s clinical description of au‐ tistic disorder suggested that excellent rote memory might be involved in its aetiology [3]. In addition, some authors have thought that S could have had an Autism Spectrum Disorder (ASD) [4,5]. So the question arises: if S could have had an ASD, then how might his memory have given rise to such an ASD? For this reason, the present chapter begins by reviewing the evidence for the diagnosis of autistic disorder in S using criteria from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Re‐ vision (DSM-IV-TR) of the American Psychiatric Association [6] and from proposed crite‐ ria for its fifth edition [7], the chapter also compares his symptoms with those from a famous case (DT) with Asperger syndrome [8,9]. It is concluded that S most likely had autistic disorder. Next, I reviewed the literature to determine whether the assumption that a superior memory may be the cause of autism symptoms would be acceptable or not. However, the data seem to show that S’s job as a professional mnemonist was asso‐ ciated instead with a gradual decrease in the severity of some of his autism symptoms [1], notwithstanding, there are great mnemonists without ASD [10,11]. Finally, an alterna‐ tive explanation regarding the possible relationship between superior memories and au‐

Abstract: Highly superior autobiographical memory (HSAM) is a recently identified ability that has been difficult to explain with existing memory science. The present study measured HSAM participants’ and age/gender matched controls’ on a number of behavioural measures to test three main hypotheses: imaginative absorption, emotional arousal, and sleep. HSAM participants were significantly higher than controls on the dispositions absorption and fantasy proneness. These two dispositions also were associated with a measure of HSAM ability within the hyperthymesia participants. The emotional-arousal hypothesis yielded only weak support. The sleep hypothesis was not supported in terms of quantity, but sleep quality may be a small factor worthy of further research. Other individual differences are also documented using a predominantly exploratory analysis. Speculative pathways describing how the tendencies to absorb and fantasise could lead to enhanced autobiographical memory are discussed.

Abstract: Much controversy has been focused on the extent to which the amygdala belongs to the autobiographical memory (AM) core network. Early evidence suggested the amygdala played a vital role in emotional processing, likely helping to encode emotionally charged stimuli. However, recent work has highlighted the amygdala's role in social and self-referential processing, leading to speculation that the amygdala likely supports the encoding and retrieval of AM. Here, cognitive as well as structural and functional magnetic resonance imaging data was collected from an extremely rare individual with near-perfect AM, or hyperthymesia. Right amygdala hypertrophy (approximately 20%) and enhanced amygdala-to-hippocampus connectivity (>10 SDs) was observed in this volunteer relative to controls. Based on these findings and previous literature, we speculate that the amygdala likely charges AMs with emotional, social, and self-relevance. In heightened memory, this system may be hyperactive, allowing for many types of autobiographical information, including emotionally benign, to be more efficiently processed as self-relevant for encoding and storage.