People With a Rare Memory Gift Can Remember Almost Every Day of Their Lives and Sleep May Explain Why

Scientists found unusual sleep rhythms in people with extraordinary autobiographical memory.

Some people can recall almost every day of their adult lives with startling precision. Give them a date, and they can often name the day of the week, what happened in the news, and what they were doing at the time.

A new sleep study suggests this rare ability, known as highly superior autobiographical memory, or HSAM, may be linked to what happens in the brain at night. Researchers found that people with HSAM had more sleep spindles — short bursts of brain activity tied to memory consolidation — especially in brain regions associated with vivid recall.

The findings do not fully explain why some people remember so much more than others. But they suggest that HSAM may not come from recording life in greater detail. Instead, these people may hold on to memories more effectively because sleep helps consolidate them more strongly.

The People Who Live With Total Recall

HSAM is not ordinary good memory. It is not the trained memory of a card champion or the product of someone who has mastered mnemonics. It is almost a complete autobiographical memory: the self filed by date, for every day of their lives.

The condition has been studied scientifically only since 2006, when researchers described the first famous case, a woman given the pseudonym “AJ.” Since then, only around 100 people have been formally confirmed, though researchers suspect more exist.

CTV’s W5 recently profiled Emily Nash, an 18-year-old from near Ottawa who was formally tested by researchers in the United States. Asked about Oct. 21, 2021, she replied almost instantly: “October 21, 2021? Oh, the Alec Baldwin ‘Rust’ shooting. That was a Thursday.”

Emily described her memory as a calendar made of moving pictures. “Each day kind of represents a little movie, where I can rewind and fast forward and replay various points throughout my day,” she said.

That sounds enviable until the darker half of the gift comes into view. People with HSAM do not only keep happy days in their heads. They also keep humiliation, grief, fear, and heartbreak with unusual force. Jill Price, one of the best-known people with HSAM, told 60 Minutes in 2010: “I can’t just move forward,” adding that living with HSAM was “detrimental to my daily life.”

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A Memory Mystery Moves Into the Sleep Lab

The new study, led by Carmen Westerberg of Texas State University with colleagues at Northwestern University, asked what happens while people with HSAM sleep.

The team brought nine HSAM individuals and 13 matched controls into the lab for two nights of polysomnography, the standard overnight recording of sleep. The first night served mostly as an adjustment period, because few people sleep naturally the first time sensors are fixed to their head and body.

The participants also completed brief tests of episodic memory and intelligence, along with questionnaires about sleep quality and daytime sleepiness. The researchers did all this because they were trying to rule out other explanations. Maybe HSAM people are just smarter. Maybe they sleep longer. Maybe they spend more time in deep sleep.

They did not.

“No group differences were observed in the neuropsychological assessments or in the subjective measures of sleep and daytime sleepiness,” the authors wrote in their study.

The groups also showed no differences in total sleep time, time spent in each sleep stage, or one common measure of slow-wave activity.

Then the researchers looked more closely.

“HSAM individuals showed higher non-REM sleep spindle density than controls at frontal, central, and parietal sites, with the largest increase at parietal sites,” the authors wrote. “Furthermore, during non-REM sleep, spindles were more precisely coupled to the peaks of the slow oscillations in HSAM individuals than in controls at parietal sites.”

The Nightly Work of Remembering

Sleep spindles are brief bursts of brain activity that appear during non-REM sleep. On an EEG, they look like little flurries in the sleeping brain’s electrical weather. To memory researchers, they are interesting because they appear to help the brain stabilize and store experience.

A simple way to think about it is this: the sleeping brain does not merely switch off. It replays, sorts, strengthens, and sometimes discards. Slow waves provide one rhythm. Spindles provide another. When these rhythms line up well, memories may be more effectively transferred into long-term storage.

In HSAM, the signal was strongest around parietal sites. That is notable because the parietal cortex is involved in the vivid sense of recollection — the feeling not just that something happened, but that one can almost re-enter it.

In other words, HSAM may not be a case of extraordinary recording at the moment of experience. The authors write that earlier research suggests HSAM is “not a result of better memory encoding.” Instead, “HSAM individuals appear to not forget as easily as other individuals.”

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Westerberg put the same idea in plainer terms to CTV: “They’re not really taking in more information. It’s just that they are not forgetting it like most people do.”

That distinction matters. Human memory is not a camera. In fact, photographic memory is a myth. Although we often see it as a failure, forgetting is part of mental housekeeping. The brain must generalize, soften, and discard. HSAM may reveal what happens when one part of that balance shifts.

A Gift, a Burden, and a Clue

The findings are small and preliminary. Nine HSAM participants are not many. But for a condition this rare, even nine is meaningful. The paper should be read as a strong clue, not a definite conclusion.

Memory loss is one of the most feared features of aging and dementia. Sleep disruption is common in cognitive decline. Researchers have long suspected that broken sleep may worsen memory problems, and that repairing sleep rhythms could help the brain hold on to experience.

That is why HSAM fascinates scientists.

“If we can figure out what’s going right with memory, maybe we can help with what’s going wrong,” Westerberg told CTV.

There are already experiments elsewhere using brain stimulation to target circuits implicated in HSAM, including trials in people with early Alzheimer’s disease. That does not mean a treatment is near. It means the science of frighteningly rich memory may one day inform the science of failing memory.

For Emily Nash, the question is also personal. Two of her grandparents had dementia. “I want to help in the best way possible with my memory,” she said.

The new study ends with cautious optimism. The results, the authors write, are “the first to demonstrate that aspects of sleep physiology previously implicated in memory consolidation” are enhanced in HSAM. They suggest that “superior memory consolidation contributes to superior autobiographical memory.”

The findings appeared in the journal Sleep.