Science

Sleep Sharpens Memory

Dozing does not just protect what we store for recall later, it also eases our retrieval of it

Open | 05 Aug, 2015

Sleep, past studies have proven, stops memories from getting forgotten. But a new study shows that sleep does not just protect memories, it also makes them easier to access. According to the scientists associated with this research, sleep makes it easier to retrieve nuggets of information that may otherwise have got lost in our brains.

The study, conducted by researchers from University of Exeter in the UK and the Basque Centre for Cognition, Brain and Language in Spain, and published in the journal Cortex, found that after sleep we are twice as more likely to recall facts which we could not remember while still awake. According to the researchers, the post-sleep boost in memory accessibility indicates that some memories are being sharpened during sleep, thereby supporting the notion that we actively rehearse information flagged by our minds as ‘important’ during sleep.

For the study, two previous studies involving 123 participants whose memories were tracked for made-up words were analysed. Subjects were asked to recall words immediately after exposure, and then again after the period of sleep or wakefulness. The key distinction was between those word memories which participants could remember at both the immediate test and the 12-hour retest, and those not remembered at test but eventually remembered at retest. Researchers found that, compared to daytime wakefulness, sleep helps one rescue unrecalled memories more than it prevents memory loss.

Dr Nicolas Dumay, one of the researchers involved in the study, explains in a press release that he believes this memory boost comes from the hippocampus, an inner structure of the temporal lobe, unzipping recently encoded episodes and replaying them to regions of the brain originally involved in their capture. This, he explains, would lead the subject to effectively re-experience the major events of the day. He says, ‘Sleep almost doubles our chances of remembering previously unrecalled material. The post-sleep boost in memory accessibility may indicate that some memories are sharpened overnight…’