Sleeping not only protects memories from being forgotten, it also makes them easier to access, according to a new study.
A researcher at the University of Exeter in England and the Basque Centre for Cognition, Brain and Language found that, after a good night’s sleep, we are more likely to recall facts that we couldn’t remember while still awake.
The study, published in the journal Cortex, tracked memories for made-up words learned either prior to a night’s sleep, or an equivalent period of wakefulness. Participants were asked to recall words immediately after exposure to the new words, and then again after a period of sleep or wakefulness.
The researcher found that, compared to daytime wakefulness, sleep helped rescue unrecalled memories more than it prevented memory loss.
“Sleep almost doubles our chances of remembering previously unrecalled material,” said Dr. Nicolas Dumay, an experimental psychologist at Exeter and an honorary staff scientist at the Basque center in Spain.
“The post-sleep boost in memory accessibility may indicate that some memories are sharpened overnight. This supports the notion that, while asleep, we actively rehearse information flagged as important.”
More research is needed, he added, especially “into the functional significance of this rehearsal and whether, for instance, it allows memories to be accessible in a wider range of contexts, hence making them more useful.”
The beneficial impact of sleep on memory is well-established, and sleeping is known to help us remember the things that we did, or heard, the previous day. The idea that memories could also be sharpened and made more vivid and accessible overnight, however, is yet to be fully explored, according to Dumay.
He added he believes the memory boost comes from the hippocampus, which unzips recently encoded episodes and replays them to regions of the brain originally involved in their capture. This leads us to effectively re-experience the major events of the day, he said.
Source: University of Exeter