Sleep Memory Research Shows Lack of Sleep Hurts Memory

Students pulling an all-nighter before the big test and adults stressing into the wee hours over that big presentation tomorrow might want to get some shut-eye, instead.

Lots of the research presented this week at Sleep 2006, a joint meeting of the American Academy of Sleep Medicine and The Sleep Research Society, says lack of sleep can sabotage memory and performance.

Sleep 2006, which concluded at the Salt Palace Thursday, was the largest gathering of sleep experts in the world.

From the pages of the 150-page program, with its lists of symposia, lectures, poster sessions, keynotes and discussion groups a theme emerged: Sleep is good, sleep disorders are bad, with implications for work performance, driving safety and overall health.

In fact, based on sleep memory research it appears that sleep is so good for recall that it competes favorably with studying and then reviewing 20 minutes later, with the added bonus that during sleep your brain may figure out associations and links for you.

That's the finding of a research project at Harvard University, where a group of researchers found sleep enhances simple memory tasks, but it also allows the brain to figure out the "gist" of something and boosts creative association.

The sleep memory researchers used word lists, carefully built around a "lure" word that wasn't included. For instance, a word list containing "thread, pin, eye, sewing, sharp, point, haystack, pain" and similar words points to the unstated word, "needle." Subjects were given eight such lists of semantically linked words to study.

Each participant was then assigned to one of four study groups, two of them control groups and the other two representing "wake" and "sleep." The wake group saw the lists at 9 a.m. and returned at 9 p.m. to recall the words for the researchers. The sleep groups saw the list at 9 p.m. and, after a good night's sleep, returned at 9 a.m. to recall the lists, according to Jessica D. Payne, Ph.D., part of the research team, which presented findings at a poster session.

The control groups showed that being a night person or a morning person didn't make a difference. But sleep itself did.

Those who got a night's sleep were much better at recalling the lists of studied words. They were, in fact, about the same as the control group that had to remember the words for only 20 minutes. And everyone knows, Payne said, that it's easier to remember things for a short time than for a long one.

But sleep also increased the chance a participant would include the unused "lure" word as part of the list, recalling, for instance, needle as one of the words on the list when it wasn't. Since the wake group was less apt to include the lure, the researchers concluded that sleep improved the brain's ability to see associations between things. That's the "gist" part of the conclusion. They also found that people who had slept on it came up with more creative word associations, as well.

The fact that the unused lure words were more likely to be "recalled" by those who slept isn't a bad thing at all, Payne said. "To me, it says the memory's working like it should," linking things together and figuring things out.

Harvard Sleep Memory Research

In other research at Harvard, scientists tackled an old question. People retain much more of what they learn after sleeping. The question is, does sleep make it better or does being awake make it worse because of all the interference and distractions? Researcher Jeffrey Ellerbogen and colleagues theorized that those who sleep well would be more resistant to interference the next day.

In their study, the interference was asking subjects to study word groups, then later introducing them to a bogus group of words, designed to do nothing more than cloud the recall. Each word group has 20 word pairs and some of those words were incorrectly paired with other words on the list designed to confuse.

Those who had sleep and no interference had very good recall. Those who had sleep and interference also did much better, compared to those who had no sleep.

"The folks with sleep did way better," he said. "Sleep actively protects memory from subsequent interference."

Other research from Harvard shows that sleep facilitates the consolidation of emotional, episodic memory, too.

It's something to sleep on.

E-mail: lois@desnews.com