According to a new study published in the journal eLife, sleep appears to increase links between three areas of the brain that are essential for reinforcing memory and processing reward.
Study authors suggest that receiving rewards as we learn can help fortify new information in memory—and daytime naps, specifically, can increase this effect.
For the study, 31 healthy volunteers were randomly assigned to either a “sleep” group or a “wake” group. Both groups were asked to look at and remember eight pairs of pictures. They were told that for four of the eight pairs of pictures, there would be a higher reward if they remembered them. Once the learning phase was complete, both groups took a 90-minute break. The “sleep” group took a daytime nap, and the “wake” group just rested.
After the break, both groups were tested on their memory of the picture pairs and were asked to score how confident they felt about giving a correct answer.
After a three month-period, a surprise test was administered. Both groups were asked to remember the picture pairs and give their confidence score.
Researchers had already established that each participant had the same sensitivity to reward, so they ruled this out as a potential influencer on the results.
Study results indicated that after the 90-minute break, the sleep group performed better. When it came to the more highly rewarded picture pairs, both groups performed equally well.
But, researchers did find a striking difference in the surprise test administered three months later: the sleep group illustrated a greater memory performance for the highly rewarded picture pairs than the wake group.
The sleep group showed higher rates of confidence of getting the right answer, even after three months. During testing when MRI testing was conducted, researchers discovered that sleep group participants had more activity in the hippocampus, the area of the brain responsible for forming memories. After the three-month period, the sleep group showed heightened connectivity between the hippocampus and other areas of the brain involved in memory association and reward processing: the striatum and the medial prefrontal cortex.
Kinga Igloi, the study’s lead author, says, “Rewards may act as a kind of tag, sealing information in the brain during learning. During sleep, that information is favorably consolidated over information associated with a low reward and is transferred to areas of the brain associated with long-term memory.”
Igloi notes that study findings may be pertinent for understanding the destructive effects that lack of sleep can have on achievement.
Sources for Today’s Article:
Paddock, C., “Daytime naps, rewards help cement memory, boost learning,” Medical News Today web site, October 19, 2015; http://www.medicalnewstoday.com/articles/301185.php.
Igloi, K., et al., “A nap to recap or how reward regulates hippocampal-prefrontal memory regulates during daytime sleep in humans,” eLife October 16, 2015, doi: 10.7554/eLife.07903#sthash.8VA5XmqD.dpuf.