Yet another study has been released telling us sleep is good for our memory, but this time it’s about recall rather than protecting memories from being forgotten. The research, coming out of the University of Exeter and the Basque Centre for Cognition, Brain and Language, suggests that we are more likely to recall facts after sleeping than we were able to recall while still awake.

The experiment tracked the memory of made-up words that were learned either prior to 12 hours of sleep, or an equivalent period of wakefulness. Participants were asked to recall the words twice, once immediately after exposure and once their 12-hour period of sleep or wakefulness had elapsed.

The results, published in Cortex, suggested that a night’s sleep promoted access to memories that had initially been too weak to retrieve.

"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," said Nicholas Dumay, of the University of Exeter, in a press release. "This supports the notion that, while asleep, we actively rehearse information flagged as important. More research is needed 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."

It’s been well known that sleep has a beneficial impact on memory, and that sleeping helps us to remember things we saw or heard the previous day. The idea that memories could become more accessible and vivid because of sleep, however, has not fully been explored.

Dumay said that he believes the boost in memory is caused by the Hippocampus, a brain structure critical to the recall of recently encoded memories.

Recall Vs. Remembering: What’s The Difference?

The way our memory works is still largely a mystery to scientists. Instead of being relegated to one area or structure of the brain, memory is a brain-wide process. Scientists generally agree on three steps in the memory process: encoding, storage, and recall. When we forget a piece of information, there are several possible reasons for it. Though the outer result may be the same to us — we can’t remember what we need to — the reason for it can be quite different each time.

One reason for loss of memory is simply a failure to encode the information in the first place. If sensory input never enters our memory in the first place, we will never be able to retrieve it. This may feel like we forgot something, but in reality, we never had it in the first place.

Retrieval failure, however, does concern memories that we successfully encoded and stored in our brains. Many reasons have been suggested to explain our occasional failure to recall, including the idea that if a memory is not periodically retrieved and rehearsed, we will lose it. This is the kind of forgetting that is going on when we have the “tip-of-the tongue” experience — we know we know something but just can’t seem to grasp it.

Source: Dumay N, et al. Sleep Not Just Protects Memories Against Forgetting, It Also Makes Them More Accessible. Cortex. 2015.