It’s been a while since my last post on sleep and learning. During that time, evidence suggesting the critical connection between sleep, learning, and memory has continued to accumulate. For a poor sleeper like me, it has also become more disturbing in some ways. Here’s a quick run down on some of the recent research.
One impact of sleep that we have known about for quite a while is that it helps us to solidify and preserve memory. That is, it helps prevent forgetting. A study published in Cortex, however, suggests that sleep may more do than just preserve memories: it may make them much more accessible to us, ensuring that we are actually able to remember when we need to.
To reach this conclusion, the study’s author, Nicolas Dumay of the University of Exeter, re-analyzed data from two previous studies to compare the impact of a period of overnight sleep to a similar period of daytime wakefulness on the ability of study participants to remember a list of made-up words. The differences in memory were significant.
“Sleep almost doubles our chances of remembering previously un-recalled material,” said Dumay. “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.”
As positive as improving our ability to preserve and access our memories may sound, it’s important to remember that there can be downsides. Namely, there is no guarantee that the memories we solidify during sleep are valid or desirable. We may, in fact, wind up more deeply learning and remembering information that is flat our wrong or significantly biased.
Fortunately, a study out of Northwestern University suggests that we can take advantage of the way sleep operates on memory to unlearn biases. Xiaoqing Hu, one of the study’s author’s writes about it in much more detail in Can we unlearn social biases while we sleep? The quick answer to the question, though, is yes. The study assessed 40 participants on their implicit biases related to race and gender. Then, following a session of counter-bias training, participants took a 90-minute nap during which sound “cues” from the training were played repeatedly, but without waking the participants.
The results were striking. Hu writes that:
the biases were reduced by at least 50% relative to the pre-sleep bias level. But we were also surprised at how long the effect lasted. At the one-week follow-up test, the sleep-based intervention was still effective: bias reduction was stabilized and was significantly smaller (approximately 20%) than its baseline level established at the beginning of the experiment.
The results of the one-week follow-up were particularly promising. In many cases, the impact of interventions like this fades away entirely within hours or days. Using sleep as a tool, though, appears to have some staying power. (You may also want to read about meditation as a way to combat bias.)
Finally, if the above items don’t motivate you to develop better sleep habits, this final one may scare you into. A study out of Berkeley suggests that a deficit of sleep can lead to a build up of the proteins that many scientist feel are responsible for Alzheimer’s disease. Getting full, restorative sleep has an opposite effective. As Matthew Walker, a Berkeley neuroscience professor and one of the study’s authors put it “Sleep is helping wash away toxic proteins at night, preventing them from building up and from potentially destroying brain cells. It’s providing a power cleanse for the brain.”
It’s important to note that, unlike most studies conducted previously in this area, the Berkeley study was conducted with human rather than animal subjects. Specifically, the participants were “26 older adults, between the ages of 65 and 81, who showed no existing evidence of dementia or other neurodegenerative, sleep or psychiatric disorders.” Also worth emphasizing is the fact that sleep is both a preventative and a therapeutic “treatment” that is well within the reach of all of us.
Of course, I know from my own experience that understanding that sleep is important and actually being able to sleep well consistently are two very different things. To that point, I do plan to pull together a post on the sleep tips that seem to have the most basis in scientific evidence. In the mean time, you may be able to take some solace from a study that suggests we may in fact be getting more sleep than we think we are.
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