Hyperthymesia

unforgettable memories

funes el memorioso

Hyperthymesia [hi-per-thy-mee-zee-uh], also known as piking, is a condition in which the individual possesses a superior autobiographical memory, meaning they can recall the vast majority of personal experiences and events in their lives.

The term ‘hyperthymesia’ is derived from the Greek words thymesis, meaning ‘remembering’ and hyper meaning ‘excessive.’ As first described in a 2006 ‘Neurocase’ article, the two defining characteristics of hyperthymesia are ‘the person spends an abnormally large amount of time thinking about his or her personal past, and the person has an extraordinary capacity to recall specific events from his or her personal past.’

Individuals with hyperthymesia can recall almost every day of their lives in near perfect detail, as well as public events that hold some personal significance to them. Those affected describe their memories as uncontrollable associations, when they encounter a date, they ‘see’ a vivid depiction of that day in their heads. Recollection occurs without hesitation or conscious effort.

It is important to draw a distinction between those with hyperthymesia and those with other forms of exceptional memory, who generally use mnemonic or similar rehearsal strategies to memorize long strings of subjective information. Memories recalled by hyperthymestic individuals tend to be personal, autobiographical accounts of both significant and mundane events in their lives. This extensive and highly unusual memory does not derive from the use of mnemonic strategies; it is encoded involuntarily and retrieved automatically. Despite being able to remember the day of the week on which a particular date fell, hyperthymestics are not calendrical calculators like some people with autism or savant syndrome. Rather, hyperthymestic recall tends to be constrained to a person’s lifetime and is believed to be an unconscious process.

Although hyperthymestics are not autistic, and likewise savants do not memorize autobiographical information, there are certain similarities between the two conditions. Like autistic savants, individuals with hyperthymesia have an unusual and obsessive interest in dates. Russian psychologist Aleksandr Luria documented the famous case of mnemonist Solomon Shereshevskii, who was quite different from the first documented hyperthymestic known as AJ in that he could memorize virtually unlimited amounts of information deliberately, while AJ could not – she could only remember autobiographical information (and events she had personally seen on the news or read about). In fact, she was not very good at memorizing anything at all, according to the study published in ‘Neurocase.’ Hyperthymestic individuals appear to have poorer than average memory for arbitrary information. Another striking parallel drawn between the two cases was that Shereshevskii exemplified an interesting case of synaesthesia (a condition where the brain mixes up the senses) and it has been suggested that superior autobiographical memory is intimately tied to time-space synaesthesia.

Hyperthymestic abilities can have a detrimental effect on cognitive capacity. The constant, irrepressible stream of memories has caused significant disruption to AJ’s life. She described her recollection as ‘non-stop, uncontrollable and totally exhausting’ and as ‘a burden.’ Like all hyperthymestics, AJ is prone to getting lost in remembering. This can make it difficult to attend to the present or future as she is permanently living in the past.

It has been proposed that the information encoded by hyperthymestics is semantic and therefore semantic cues are used in retrieval. Once cued, the memory is retrieved as episodic and follows a pattern similar to that of a spreading activation model. This is particularly evident AJ’s case. She describes how one memory triggers another, which in turn triggers another and how she is powerless to stop it: ‘It’s like a split screen; I’ll be talking to someone and seeing something else.’ This theory serves to explain why hyperthymestics have both a sense of ‘knowing’ (semantic memory) and ‘remembering’ (episodic memory) during recollection. Hence, hyperthymesia is essentially superior semantic autobiographical memory.

Individuals with hyperthymesia often display OCD tendencies. AJ reports that from a young age, she would become upset when order in her environment was disturbed. She kept a daily diary for 32 years as a way of maintaining control over her environment. Hoarding behavior is also common, AJ collects TV guides. This obsessive-compulsive nature may be facilitating consolidation of memories and could explain the unconscious use of dates as organized mnemonic devices.

The theory that hyperthymestic abilities could be attributed to a failure in our cognitive capacity to forget superfluous information has been suggested by numerous researchers. Parker et al report on how executive difficulties, such as lack of inhibition, may explain the constant and unstoppable memory retrieval. ‘It is, however, quite possible that there is no causal relationship and that the overall parallels between her memory and her neuropsychological weaknesses are simply correlative.’

An MRI study conducted on AJ provides a solid argument as to the neurological foundation of her superior memory. Both the temporal lobe and the caudate nucleus were found to be enlarged. The hippocampus, located in the medial temporal lobe, is involved in the encoding of declarative memory (memory for facts and events), while the temporal cortex is involved in the storage of such memory. The caudate nucleus is primarily associated with procedural memory, in particular habit formation, and is therefore intrinsically linked to Obsessive Compulsive Disorder. Parker and colleagues speculated that a defective frontostriatal circuit could be responsible for the observed executive function deficits in hyperthymesia. This circuit plays a crucial role in Neurodevelopmental disorders such as ASD, OCD and ADHD. Given the parallels in some aspects of behavior, it is possible that AJ’s hyperthymestic abilities stem from atypical neurodevelopment.

The debate as to whether hyperthymestic syndrome can be considered a distinct form of memory is ongoing. K. Anders Ericsson of Florida State University does not believe that there is sufficient evidence to suggest that AJ’s skills need additional explanation: ‘Our work has pretty much concluded that differences in memory don’t seem to be the result of innate differences, but more the kinds of skills that are developed.’

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