Science News

A good nightís sleep may make bad memories worse

Sun, 22nd Jan 2012

Hannah Critchlow

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A study published this week in the Journal of Neuroscience indicates that sleep can reinforce unpleasant memories. Remaining awake, on the other hand, helps you to forget.

University of Massachusetts, Amherst scientist Rebecca Spencer and her colleagues showed groups of volunteers a series of images and asked them to rate how emotionally harrowing they were.

A sleeping boy12 hours later, after one group had been allowed to sleep for 8 hours, whilst the other group were forced to stay awake, the volunteers were then asked to reexamine the pictures.

Those who slept were much better at remembering which images they had already seen compared with those who stayed awake. 

Not only that, but those who slept still rated the images to be as, if not more, traumatic as the first time they saw them. Those who stayed awake, on the other hand, found the images to be less harrowing after 12 hours.

The researchers controlled for the fact that the sleep deprived group were not simply too tired to respond to the pictures emotionally by repeating the experiment at different times of day.

These results may explain why some people can find it difficult to fall asleep after a traumatic experience, because this is the brains way of stopping you remembering something that would be better off forgotten.

So, contrary to the prevailing view that Ďall will seem better after a good nightís sleepí Ė this might actually be the opposite of Ďwhat the doctor orderedí for people exposed to traumatic events. 



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A listener got in touch after hearing this story saying:

Hello ,

In the news section of the 22nd Jan 2012 podcast , there is an article that talks about sleep and emotions or memories .

But I have previously read an article on a website about the same subject

and Iím really confused .

Iím sorry , Iím not an expert or something . I did not understand the whole thing

and I just thought you might help me .

By the way , Iím new to The Naked Scientists podcast and I like it very much

I would be grateful if you could respond to my message .


We asked Rebecca Spencer, lead author of the study and she replied:

Hi Hannah,

The simplest answer is that we measure something totally different.  We're most interested in how sleep changes emotion on a negative to neutral to positive scale, in other words, how emotionally negative is it.  The type if emotion (neg, pos, neutral) is ignored in Walker's work instead the rate just "intensity" regardless of emotion type.  Note that Walker also did not measure the relationship with memory either even though his model makes predictions regarding the interaction of memory and emotionality changes.

The perhaps more complicated part of the answer is that in addition to measuring subjective valence (negative->neutral) we measured arousal.  We saw no sleep effects on arousal yet this measure should most closely match Walker's measure if "intensity".  If it's the case that these capture the same construct, then I would turn to analytical or methodological differences across our studies.  They analyzed their data in an much different......way too.  For this reason, you will see a link to supplementary materials at the end of our paper.  In these materials, we plot our data using their approach and we still don't agree.  So then you could turn to methodological differences.  If I remember right (I don't have the Walker paper with me) they combine negative and positive images and we know how you process a negative item in a positive context will be different than if just paired with neutrals  They also use stimuli of a much different range of valence and arousal (if I remember right, much more mild than ours). 

All in all, it's up to both of our labs to continue to sort this out and I do believe we will! 

I hope this helps!


So they are measuring different things, hence they get different results. The relationship between sleep, emotion and memory is an area of great interest to neuroscientists, mainly because it is such a puzzle, something that they are trying to understand more about.

Looking at differences in results from studies employing different paradigms will, hopefully, help to tease out our eventual full understanding of the area.

nakedhannah, Wed, 4th Apr 2012

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