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Exceptional memory

Types of accurate and detailed recall

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Through Recall (memory), Mnemonic and Schizophrenia

Hyperthymesia

Hyperthymesia, or hyperthymestic syndrome, is superior autobiographical memory, the type of memory that forms people's life stories. The term hyperthymesia is derived from the Modern Greek word thýmesē 'memory' and Ancient Greek hypér 'over'.

The capabilities of the affected individuals are not limited to recalling specific events from their personal experience. Hyperthymesia has both enhanced autobiographical and episodic memory. There is an important characteristic of hyperthymesia: People with the syndrome have an unusual form of eidetic memory to remember as well as recall any specific personal events or trivial details, including a date, the weather, what people wore on that day, from their past, almost in an organized manner.

Unlike other people with advanced memory abilities, such as savant syndrome (who tend to use calendrical calculation), individuals with hyperthymestic syndrome rely heavily on their personal "mental calendar", which is an automatic and obsessive process. Moreover, individuals with hyperthymesia do not focus on practiced mnemonic strategies. For example, "AJ", who has the first documented case of hyperthymesia, has difficulty consciously applying her memory strategies to help her memorize new knowledge, making her rote memorization abilities below average. Importantly, having superior autobiographical memory does not translate to broadly superior memory; in fact across tests like a digit span, visual reproduction, and word-pair memorization, those with hyperthymesia have no statistically significant difference from a control group.

Neuroscience

Because it is a recently discovered memory capability, neuroscientific explanations of hyperthymesia are scarce. McGaugh, who coined the term, provides mostly speculation in "A Case of Unusual Autobiographical Remembering". He suggests that "AJ"'s superior autobiographical memory is largely the result of specific impairments rather than enhancements. Her sensitivity to cues that trigger her memories suggest that "AJ" has trouble inhibiting episodic-retrieval mode, which is the neurocognitive state required for present stimuli to be interpreted as memory cues. Because she is unable to "turn off" her retrieval mode, the smallest associations may bring on detailed recollections of "AJ"'s past.

Inhibition in itself is a type of executive functioning, thought to be associated with the right inferior frontal cortex. Although "AJ" is not autistic, McGaugh and colleagues note that she shares some of the executive-functioning deficits that occur with autism. These deficits, along with anomalous lateralization and "AJ"'s obsessive–compulsive tendencies, point to a neurodevelopmental frontostriatal disorder common in autism, OCD, ADHD, Tourette's syndrome, and schizophrenia. The frontostriatal system is made up of the dorsolateral prefrontal cortex, lateral orbitofrontal cortex, cingulate, supplementary motor area, and associated basal ganglia structures.

Cases

As of April 2016, there are an estimated 61 confirmed cases of hyperthymesia worldwide. Cases of hyperthymesia differ from related cases of savant memory in that savants have an extraordinary memory for specific hobbies, and events of a narrow basis, whereas cases of confirmed hyperthymesia show surprisingly detailed memory for specific and general events.

One subject, given any date in history, can recall what the weather was like on said date, personal details of their life at the time, and other news events that occurred at that time. Details of what the subject recalls may be significant to them in some way, but they may not be. Personal meaning does not seem to affect the subject's memory – they simply recall everything. In another confirmed case, the subject, when shown a photograph from his past, can recall the date it was taken, where it was taken, what they had done that day, and even more detailed information such as the temperature on said day.

Drawbacks

While many would consider hyperthymesia a positive trait, those with hyperthymesia also describe experiencing negative consequences of their enhanced memory. For example, one individual describes their memory as a "running movie that never stops". Furthermore, they describe viewing the world in "split screen", with the past constantly playing at the same time as the present. Similarly, the individual's superior memory does not seem to be due to a desire to apply memorizing techniques; their memorization of autobiographical information is non-conscious. Another negative aspect of hyperthymesia is that it could possibly stem from traumatic experiences in childhood in which the individual feels a need to organize memories, relive the past, and otherwise think about previous experiences more. One with exceptional memory can also recall unwanted events in great detail, such as being able to relive past traumatic events in their life, which can enhance the effects of the trauma.

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