Sleep and memory are loving bedfellows. Sleep "blocks" our brain's mechanisms of forgetting, lowering the neurotransmitter dopamine, and therefore facilitating memory formation.
Furthermore, recent studies have revealed that sleep is key for consolidating memories that we made while awake, as well as for preserving the brain's ability to learn new things in the future.
For instance, a study revealed that during sleep, our synapses relax, staying supple and flexible, which maintains our brain's neuroplasticity and ability to learn.
On the other hand, poor sleep leads to rigid synapses and an impaired ability to learn new things in the long run.
Perhaps even more surprisingly, researchers have recently been able to interfere with the memory consolidation process that takes place during sleep by scanning people's brains, selectively choosing certain memories, and reinforcing them.
But could a state of simple, restful wakefulness be just as beneficial for new memory formation? A new study — jointly conducted by Michael Craig, a research fellow at the Heriot-Watt University in Edinburgh, United Kingdom, and Michaela Dewar, a research leader and assistant professor at the same university — suggests that it can.
"Recent research," says Craig, "suggests that the memory system strengthens weak new memories by 'reactivating' them, where brain activity first observed during learning automatically reappears in the minutes that follow."
Based on the findings of their own research, the scientists say, "This appears especially true during sleep and quiet resting, when we're not busy taking in any new sensory information."
What's more, the new research suggests not only that a period of quiet restfulness helps us to remember new things, but that such a rest is crucial for retaining the fine details.
The new findings were published in the journal Nature Scientific Reports.
Studying fine memories
Craig and Dewar designed a memory test to assess the ability to retain finely grained information. They asked 60 young male and female participants — aged 21, on average — to look at a set of photos.
They were asked to discern between "old" photos and "similar" ones. If the participants' ability to retain fine nuances was good, they would say the photos were "similar."
"However," explains Craig, "if not-so-detailed memories are stored, people should miss the subtle differences in similar photos, and mistake them for 'old' photos."
He goes on to summarize these "interesting" findings, saying, "Younger adults who quietly rested in the minutes that followed the photo presentation were better at noticing subtle differences in similar photos."
This, he explains, suggests "that these individuals stored more detailed memories, compared to those who did not rest."
"This new finding provides the first evidence that a brief period of quiet rest can help us to retain more detailed memories."
He adds, "We think that quiet resting is beneficial because it is conducive to the strengthening of new memories in the brain, possibly by supporting their automatic reactivation."
However, Craig admits that the mechanisms behind this surprising phenomenon remain a mystery.
"[W]e don't know exactly," he goes on to conclude, "how this rest-related memory strengthening works. Specifically, it remained unknown whether quiet resting only allows us to retain more information, or whether it also helps us to retain more detailed memories."