Hyperthymesia

Hyperthymesia is the condition of possessing an extremely detailed autobiographical memory. People with hyperthymesia remember an abnormally vast number of their life experiences.

American neurobiologists Elizabeth Parker, Larry Cahill, and James McGaugh (2006) identified two defining characteristics of hyperthymesia: spending an excessive amount of time thinking about one's past, and displaying an extraordinary ability to recall specific events from one's past.^[1] The word "hyperthymesia" derives from Ancient Greek: hyper- ("excessive") and thymesis ("remembering").

Signs and symptoms

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.^[3] 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.^[4] 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 a subconscious process.

Although hyperthymestics are not necessarily autistic, and likewise savants do not necessarily memorize autobiographical information, certain similarities exist between the two conditions. Like autistic savants, some individuals with hyperthymesia may also have an unusual and obsessive interest in dates. Russian psychologist Aleksandr Luria documented the famous case of mnemonist Solomon Shereshevskii,^[5] who was quite different from the first documented hyperthymestic known as AJ (real name Jill Price) in that Shereshevskii 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.^[1] 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 synesthesia^[6] and it has been suggested that superior autobiographical memory is intimately tied to time-space synaesthesia.^[7]

Difficulties

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".^[1] 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.

AJ displays considerable difficulty in memorizing allocentric information. "Her autobiographical memory, while incredible, is also selective and even ordinary in some respects," – McGaugh.^[1] This was demonstrated by AJ's poor performance on standardised memory tests. At school, AJ was an average student, clearly unable to apply her exceptional memory to her studies. Similar patterns have been observed in other cases of hyperthymesia.

Deficits in executive functioning and anomalous lateralisation were also identified in AJ. These cognitive deficiencies are characteristic of frontostriatal disorders.^[1]

Causes

Due to the scarcity of hyperthymestic individuals, relatively little is known about the processes governing this superior memory ability.

Psychological

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 in 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."^[1] This theory serves to explain why hyperthymestics have both a sense of 'knowing' (semantic memory) and 'remembering' (episodic memory) during recollection.

Others suspect that hyperthymesia may be a result of reviewing memories constantly to an obsessive-compulsive degree.^[8] Other findings have shown that the tendencies to absorb new information and fantasize are personality traits that are higher in hyperthymestics than the rest of the population. These traits: absorption and fantasizing also correlated with one of the tests that measures superior autobiographical memory within the hyperthymestic sample.^[9]

Biological

An MRI study conducted on AJ provides a plausible argument as to the neurological foundation of her superior memory.^[10][11] 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.^[12] 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. Given the parallels in some aspects of behavior, AJ's hyperthymestic abilities possibly stem from atypical neurodevelopment.

This evidence provides significant support both for the extraordinary memory abilities and the behaviors of hyperthymestics. Scientists now need to ascertain if and how these brain areas are connected to establish a coherent neurological model for superior autobiographical memory.

Diagnosis

Parker and colleagues used a variety of standardised neuropsychological tests in their diagnosis of AJ's hyperthymesia. These included tests of memory, lateralisation, executive functions, language, calculations, IQ, and visual-spatial and visual-motor functions.^[1] They also devised novel tests to examine the extent of her memory abilities. These mostly consisted of questions pertaining to specific dates and events in history. Some of her personal recollections were verified with diary entries, as well as by her mother.^[1]

More recently, neuroscientist David Eagleman at Baylor College of Medicine developed a free on-line test for hyperthymesia.^[13] Participants first give their year of birth, and then are challenged to match dates to 60 famous events that happened between the time they were five years old and the present day. To qualify as potentially hyperthymestic, participants must achieve a score at least three standard deviations above the average. To prevent people from searching for answers on-line during the test, reaction time for each question is measured; answers must be chosen within 11 seconds to qualify for consideration. However, many of the questions are sourced in American culture and test results could have a strong cultural bias against non-Americans.

Society and culture

Notable cases

As of November 2013, 25 cases of hyperthymesia have been confirmed in peer-reviewed articles,^{[1][2][14][15]} the first being that of "AJ" (real name Jill Price) in 2006. More cases have been identified that are yet to be published.^[16] AJ's case was originally reported by researchers from the University of California, Irvine, Elizabeth Parker, Larry Cahill, and James McGaugh, and is credited as being the first case of hyperthymesia. AJ can apparently recall every day of her life from when she was 14 years old: "Starting on February 5th, 1980, I remember everything. That was a Tuesday."^[10]

In March 2009, AJ was interviewed for an article in Wired magazine by Gary Marcus, a cognitive psychologist at New York University.^[17] Price's brain had been subject to a brain scan and the hippocampus and prefrontal cortex had been reportedly normal. Marcus claimed, however, that her brain resembled "those of people with obsessive-compulsive disorder" and suggested that her remarkable memory might be "the byproduct of obsession", claiming also that "the memory woman clings tightly to her past". Price has since reacted angrily to such claims and McGaugh has also expressed skepticism about this explanation.^[18] Price gave her first interview in over a year for the UK's Channel 4 documentary The Boy Who Can't Forget, and provided an insight into just how difficult life can be for people who have this ability.^[18]

As the condition has become better known, more people claiming to have hyperthymestic abilities have emerged. In the aftermath of the 2006 Neurocase publication alone, more than 200 people contacted McGaugh; however, only a handful of cases were determined to be actual cases of hyperthymesia. The second verified case was Brad Williams,^[19][20][21] the third was Rick Baron,^[22] and in 2009, Bob Petrella became the fourth person diagnosed with hyperthymestic syndrome.^[23]

On December 19, 2010, actress Marilu Henner was featured on the US television program 60 Minutes for her superior autobiographical memory ability. Henner claimed she could remember almost every day of her life since she was 11 years old.^[24][25] The show was initially pitched as a story featuring hyperthymestic violinist Louise Owen, but the reporter Lesley Stahl volunteered her friend Henner as having a similar ability.^[3]

In June 2012, the case of H.K. Derryberry was reported, a blind 20-year-old man who could clearly recall every day of his life since the age of about 11.^[15] Derryberry had been born at 27 weeks, weighing just over 2 pounds (0.91 kg) and was in neonatal intensive care for 96 days. A severe brain hemorrhage was the likely cause of cerebral palsy, and his prematurity resulted in congenital blindness.^[26] He told researchers that his memories are rich in sensory and emotional details, regardless of whether they are from years ago or yesterday. About 90% of his memories are in the first person, compared with an average of 66% in the general population. Brandon Ally and his team, at Vanderbilt University, Nashville, Tennessee, conducted a series of tests with the subject, including a brain scan which was compared with 30 age-matched controls. His brain was smaller than average (probably a result of his premature birth at 27 weeks). His right amygdala, however, was 20% larger, with enhanced functional connectivity between the right amygdala and hippocampus and in other regions.^[27]

In September 2012, UK's Channel 4 screened the documentary The Boy Who Can't Forget, which examined the memory of 20-year-old Aurelien Hayman from Cardiff, a student at Durham University, who remembers practically every day of his life from the age of 10.^[18] Hayman is the first British person to be identified as possessing this ability, and he views it positively.^[28] When Hayman's brain was scanned by a team led by Professor Giuliana Mazzoni at the University of Hull, whilst he was prompted to remember a series of dates, a series of "visual areas" of the brain were activated, with much greater speed than would be expected in normal brain function. Potential problems with total recall were illustrated.^[16][29] The documentary also featured 62-year-old TV producer Bob Petrella, whose memory has allowed him to catalogue the events from his "favorite days" over many years into an extensive scrapbook.^[30]

In January 2016 painter and polymath Nima Veiseh was featured by the BBC for his use of hyperthymesia to create paintings that could only be produced with his ability.^[31] Veiseh claimed he could remember almost every day of his life since he was 15 years old, and that his ability to synthesize time and an "encyclopedic knowledge of the history of art" enabled him to create wholly unique visions on canvas. In March 2016 NPR examined further Veiseh's exploration of time and the human experience through art.^[32]

Controversies

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 sufficient evidence exists to suggest that the skills of AJ and Williams 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."^[33]

McGaugh rejects the idea that hyperthymestic syndrome can be explained away so easily; he argues that nothing explains how subjects are able to memorise so much: "You'd have to assume that every day they rehearse it... The probability of these explanations dwindles as you look at the evidence."^[33]

Cases of hyperthymesia have forced many people to re-evaluate what is meant by "healthy" memory: "it isn't just about retaining the significant stuff. Far more important is being able to forget the rest."^[33]

Significant debate also exists over the limits of memory capacity. Some are of the view that the brain contains so many potential synaptic connections that, in theory at least, no practical limit exists to the number of long-term memories that the brain can store. In 1961, Wilder Penfield reported that specific stimulation of the temporal lobes resulted in vivid recollection of memories. He concluded that our brains were making "continuous, effortless, video-like recordings" of our experiences, but that these records are not consciously accessible to us.^[34] However, a study published in the Proceedings of the National Academy of Sciences suggested that those with hyperthymesia may reconstruct memories from traces and incorporate post event information and associations—a finding at odds with Penfield's video-like recording analogy.^[14]

Appearance in fiction

• In the 2014 film The Dark Place, the protagonist of the story, Keegan Dark, has hyperthymesia. A mystery-thriller with dramatic overtones, Keegan's hyperthymesia is shown to have caused significant pain in his family life, as his inability to forget childhood and adolescent traumas has put him at odds with his parents, siblings, and friends. It has also becomes an advantage, with Keegan using it to solve the mystery at the heart of the story. The hyperthymesia memories are visually depicted in the movie as "screens" appearing to Keegan, often in an overwhelming and distressing manner.^[35]

• In the 2015 novel Memory Man by David Baldacci, the protagonist, Amos Decker, has hyperthymesia. In the book, a mystery-crime scene-thriller with graphic scenes, Decker uses his perfect memory brought on by a traumatic hit in football to solve the murder of his wife and child, and the school shooting connected to it. Decker recalls his memories as a "VCR", just playing when it wants to, or being rewound and played forward by conscious thought.

See also

• Daniel McCartney
• Hypermnesia

References

External links

• Alix Spiegel (2013-12-27). "When Memories Never Fade, The Past Can Poison The Present". NPR.  (featuring testimonials from persons with hyperthymesia)
• The Extraordinary Memory Test from David Eagleman's laboratory