More Evidence that Naps Help Memory

I have mentioned before the value of naps for improving the formation of memories. Another recent student confirms this conclusion. Matthew Walker and colleagues an the University of California at Berkeley divided 39 young adults into two groups. At noon, all the participants took part in a memory exercise that required them to remember faces and link them with names. Then the researchers took part in another memory exercise at 6 p.m., after 20 had napped for 100 minutes during the break.

Those who remained awake performed about 10 percent worse on the tests than those who napped, Walker said. Students take note: 10% can be the difference between an A and a B.

Source: Walker, Mathew. 2010. Current Models of Mechanisms of Sleep-Dependent Memory Presentation at the annual meeting of the American Association for the Advancement of Science meeting, San Diego, Feb. 21.

Caffeine or Nap: Which Helps Memory?

Caffeine gets our brain pumped up. We are more alert and perhaps should remember things better. Naps have recently been found to help the memory consolidation process. Until now, nobody has made a direct comparison of these two factors in the same people under identical conditions. But Sara Mednick and her colleagues at the University of California, San Diego, now report some helpful findings.
They tested caffeine in a single dose of 200 mg (roughly equivalent to 2-3 cups of coffee) and compared with an episode of napping (60-90 min) or placebo on the effects on performance on three types of memory tasks. For verbal memory, they tested recall and recognition memory of word lists 7 hours after learning, with an intervening nap, caffeine dose, or placebo. In addition, they conducted memory tests for a finger tap and texture discrimination task.They also conducted short-term memory on a different set of words after the first experiment.
Compared with either caffeine or placebo, naps were more effective in the word recall test, both in the consolidation test and in the short-term memory condition. Caffeine actually impaired word recall in the short-term memory task, even though the caffeine had been given some seven hours earlier. Naps also improved recognition memory in the consolidation test and recall of the texture discrimination learning. For the finger-tap learning, naps were ineffective and caffeine markedly impaired performance. The caffeine group did feel less sleepy in the late afternoon immediately prior to the memory testing, but that did not help their memory performance.
What I take from this is that the morning coffee may help you awaken, but don’t count on it to improve your memory. Other research does show that caffeine enhances mood and alertness, reaction times and speed, but don’t count on it to help your memory for things you learn that day. Note to students: all-night study sessions are a bad idea for lots of reasons and probably made much worse by drinking lots of coffee. Note to bosses: letting workers take an afternoon snooze might be a good idea.

Source:
Mednick, S. C. et al. 2008. Comparing the benefits of caffeine, naps, and placebo on verb al, motor and perceptual memory. Behavioural Brain Research. 193: 79-86.

Need to Learn Something Quickly? Try a Nap

Daytime naps are said to rejuvenate energy and lower stress. Now there is evidence that naps speed up consolidation of memories. Maria Korman and her group at the University of Haifa evaluated consolidation of a procedural memory task of learning to bring the thumb and finger together in a specific sequence. Half of the subjects were allowed to take an afternoon 90-min nap after training, while the other group stayed awake. The group that napped showed a distinct improvement in task performance when tested that evening. After a night's sleep, both groups showed the same improvement in acquired skill. So, it would appear that the nap just speeded up the consolidation process, rather than improving on the improvement that a regular night's sleep can produce.

The role of napping on interference effects was also tested. We know from numerous studies that consolidation of new learning is easily disrupted by distracting or other new learning experiences. In this experiment, another group of subjects learned a different thumb-to-finger movement sequence two hours after practicing the first task. Learning a second task right after the first was expected to interfere with learning of the first task. This proved to be the case; there was no improvement in performance of the first task either that evening or the next day after a normal night's sleep. However, based on the findings of the first experiment where a nap speeded up consolidation, the experimenters created yet another group of subjects that were allowed a 90-min nap between learning the first movement task and the second movement task. In this case, performance on the first task was improved when they were tested the next day after a normal night's sleep. Thus, the nap actually prevented the otherwise memory disrupting effect of a second learning task, presumably because the nap speeded up memory consolidation of the initial learning so that it was resistant to interference effects.

There are practical implications here, at least for procedural memories. This study indicates that if you need to learn a "how to" kind of task quickly, you should take a nap just afterward. One perhaps trivial illustration might be for football coaches who introduce some new training in the morning of a game to be played later that evening. After the morning workout, they should let the players take a nap that afternoon. Or for "two-a-days" workouts in the summer, maybe players need a nap between sessions, not just to rest but to consolidate the training.

Source: Korman, M. et al. 2007. Daytime sleep condenses the time course of motor memory consolidation. Nature Neuroscience. 10 (9): 1206-1213.