Sleep On It: Research Reveals How Sleep Can Improve Memory
There are many reasons why getting a good night’s sleep before a big test or exam is important, from heightened concentration to reduced stress levels, and recently, researchers added another incentive to the list; improved memory.
The study, which was published in the journal Nature Neuroscience, found that the more we value a piece of information, the more likely we are to review it during our sleep, and as a result, we’ll remember it better.
However, the researchers also discovered that even information that one might not normally consider to be “high value” can be reviewed during sleep with the help of some appropriate auditory stimulation.
Scientists have known for some time that sleep can play an important role in memory consolidation, but this study was the first to look at whether the reactivation of low-value memories can be encouraged so that they are also remembered later on.
In one experiment, the researchers from Northwestern University studied how participants remembered the locations of objects on a computer screen.
Each object was assigned a different monetary sum that participants would receive if they were able to remember its location later on in the test. The pay-off for some objects was much higher than for others. In this way, the researchers were able to manipulate the value of the memories.
Objects were also accompanied by a characteristic sound; for example, a picture of a cat paired with a distinctive meow or a shattered wine glass with the sound of breaking glass.
About 45 minutes after participants had memorized the objects’ location by repeatedly placing them in their assigned places; they reclined in a quiet darkened room. Electrodes attached to their scalp measured brain activity to indicate sleep or wakefulness.
While asleep, participants were unknowingly presented with some of the sounds they had heard during the test.
Later, when participants were again asked to place the objects, the researchers found that those who had been presented with the corresponding sounds while asleep were able to remember the correct locations more accurately.
“The research poses provocative implications about the role memory reactivation during sleep could play in improving memory storage,” commented Professor Ken Paller, director of the Cognitive Neuroscience Program at Northwestern University and co-author of the study.
“Whatever makes you rehearse during sleep is going to determine what you remember later, and conversely, what you’re going to forget.”
Paller points out that the selectivity of memory consolidation is not yet well understood, with most research on memory focusing on what happens when a memory is first formed and retrieved.
“The in-between time is what we want to learn more about, because a fascinating aspect of memory storage is that it is not static,” he said.
“Memories in our brain are changing all of the time. Sometimes you improve memory storage by rehearsing all the details, so maybe later you remember better — or maybe worse if you’ve embellished too much.
The fact that this critical memory reactivation transpires during sleep has mostly been hidden from us, from humanity, because we don’t realize so much of what’s happening while we’re asleep.”
The researchers add that much work still remains to determine whether the results of the study translate to other contexts, and point out that more experiments about memory processing during sleep are certain to follow.