Academic Reading: 3

Sleep and Memory

For a long time, sleep was viewed simply as a period of rest during which the brain and body recovered from the activities of the day. Over the past few decades, however, researchers have discovered that sleep plays a far more active role, particularly in the process of learning. While a person sleeps, the brain does not simply switch off; instead, it works to organize and strengthen the information gathered during waking hours.

Sleep is not a single, uniform state but consists of several stages that repeat in cycles throughout the night. Two stages in particular appear to be important for memory: deep sleep, sometimes called slow-wave sleep, and rapid eye movement (REM) sleep, during which most dreaming occurs. During deep sleep, the brain appears to replay patterns of activity that were recorded earlier in the day, effectively rehearsing new information without any conscious effort. REM sleep, on the other hand, seems to help connect new information with things a person already knows, which may explain why creative solutions to problems sometimes appear after a good night's sleep rather than during focused daytime effort.

Several experiments support the idea that sleep actively strengthens memory rather than merely preserving it. In one well-known type of study, participants learn a list of words or a physical skill, such as a sequence of finger movements, and are then tested after either staying awake or sleeping for a similar period. In most cases, the participants who slept perform noticeably better on the later test, even though they had no additional opportunity to practice. Based on findings like these, many sleep researchers now recommend that students avoid staying up all night to study before an exam. Cramming through the night may allow a person to review material one extra time, but it removes the very process, sleep, that the brain relies on to convert that information into a lasting memory.