Thursday, 2 September 2010

The woman whose new memories are erased each night

Psychologists have documented what they believe to be a clinical first - the case of an amnesic woman whose memory for new material is erased each night that she goes to sleep (movie fans will recognise this as a plot device in the 2004 film 50 First Dates. 2013 update: this is also the premise of the hit novel Before I Go To Sleep). Referred to as case FL, the woman developed these symptoms after she hit her head in a car accident in 2005, aged 48. Brain scans and neurological exams revealed no signs of brain damage, thus suggesting the woman is exhibiting what's known as psychogenic or functional amnesia - that is, symptoms in the absence of any detectable organic cause.

FL claims that on any given day her memory for newly acquired material is fine until she has a night's sleep, during which the new memories are erased (unlike standard cases of psychogenic amnesia, she says her memories from before her accident are preserved). FL's performance on lab-based memory tests was largely in keeping with her claims, with one key exception. Christine Smith and her team deployed some trickery, intermingling test items (scenes) from earlier in the day with items from previous days. FL's memory for items that she thought were from earlier in the day, but were actually seen on earlier days, was intact and comparable to the memory performance of healthy controls.

So was FL faking it, perhaps in pursuit of a compensation claim? Smith's team don't think so. Although healthy controls who were asked to fake FL's symptoms performed similarly on the memory tests, there were also differences. For example, unlike the healthy fakers, FL showed deficits in motor learning, and her confidence for test items dropped with repeated testing whereas theirs increased.

The researchers' theory is that FL truly believes she has the memory deficit that she describes and that unconscious processes may be involved in its manifestation. FL denied having seen the film 50 First Dates, which was released a year before her accident. However, she admitted that the film's female lead, Drew Barrymore, was her favourite actress, so she may have been aware of its plot. The film 'may have influenced FL's concept of how memory could fail after a car accident', the researchers said. 'The brain uses preexisting concepts of memory and through altered brain function creates a particular constellation of symptoms.'

What about treatment? Reassuring FL that evidence had been found for the intact functioning of her overnight memory proved unsuccessful. What did work was testing the limits of FL's memory-washing system. Thirty-six hours without sleep and her memories were okay. An hour's nap during the day and they were okay. In the end, it was established that FL can sleep at night for up to four to six hours at a time without experiencing the sense that she's lost the day's memories. By setting an alarm each night to wake her after bouts of three and a half hours sleep, FL has managed to overcome her strange condition. 'At our most recent contact (March 2010), she and her husband reported that she continues to use this regimen successfully,' the researchers said.
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ResearchBlogging.orgSmith, C., Frascino, J., Kripke, D., McHugh, P., Treisman, G., & Squire, L. (2010). Losing memories overnight: A unique form of human amnesia. Neuropsychologia, 48 (10), 2833-2840 DOI: 10.1016/j.neuropsychologia.2010.05.025

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

--Further reading--
A sceptical look at this case.
Real life cases of amnesia that are stranger than fiction.

6 comments:

  1. Anonymous8:29 am

    I also recall the memory being rewritten every day as the plot device in Memento.
    There is another one with a police officer who has to hide this condition so he can testify in a trial. But I cannot remember the title.

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  2. Hi Anonymous, no the character in Momento simply has difficulty laying down new memories - just as is typically found in real life amnesia. The odd thing about FL was that her memory was fine during any given day, it was only when she slept at night that her new memories were erased.

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  3. It's possible that I'll wake up in the morning and not remember what was in this post.

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  4. Great post!

    The Memento plot was based on the case of HM patient. It's a pitty that he died some time ago. You could check him out on wiki: http://en.wikipedia.org/wiki/HM_%28patient%29

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  5. Wow! I thought there's no such thing.

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  6. Anonymous6:12 pm

    Anyone interested in another opinion of this should read: Merckelback, Merten and Lilienfeld (2011) A sceptival look at a remarkable case report of overnight amnesia, sceptical Inquirer.

    ReplyDelete

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