Scientists uncover why certain memories linger
Experts have established how experiences become permanent memories, but they have now looked into why some memories are deemed important enough to linger.
A new study, which was led by researchers at NYU Grossman School of Medicine, has proposed that a mechanism in the brain decides which experiences are important enough to become permanent memories.
Published online in the journal Science, experts found that if an experience provokes enough of a reaction from somebody and they need to pause to reflect on it, the likelihood of it becoming a permanent memory is higher.
Senior study author, György Buzsáki, MD, PhD, said: ‘Our study finds that sharp wave-ripples are the physiological mechanism used by the brain to ‘decide’ what to keep and what to discard.’
Buzsáki and his colleagues had previously established that no sharp wave-ripples, which happen in the brain to signal stimuli, occur as we actively explore sensory information or move, but only during the idle pauses before and after.
Against this backdrop, the current study discovered that sharp wave-ripples represent the natural tagging mechanism during such pauses after waking experiences, with the tagged neuronal patterns reactivated during post-task sleep.
To conduct the research, scientists examined mice whose cells in the brain changed constantly over time despite them being exposed to very similar experiences. For the first time, this revealed that ripples occurred during waking pauses, and then were replayed during sleep.
Sharp wave-ripples were typically recorded when a mouse paused to enjoy a sugary treat after each maze run. The consumption of the reward, say the authors, prepared the brain to switch from an exploratory to an idle pattern so that sharp wave-ripples could occur.
‘We worked to take the external world out of the equation, and looked at the mechanisms by which the mammalian brain innately and subconsciously tags some memories to become permanent,’ said first author Wannan (Winnie) Yang, PhD, a graduate student in Buzsáki’s lab. ‘Why such a system evolved is still a mystery, but future research may reveal devices or therapies that can adjust sharp wave-ripples to improve memory, or even lessen recall of traumatic events.’
Image: Bret Kavanaugh
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