Questions & Answers: Does sleep enhance learning?

Questions & Answers

Q. Does sleep enhance learning and memory? Is there a price to pay for cutting down on the hours you sleep?

A. Scientists have long known that getting a good night's sleep helps us learn and remember. Evidence is mounting that the sleeping brain actively consolidates memories. The memories laid down by the sleeping brain are of two kinds. Declarative memory is memory for information — facts, dates, and names. Procedural memory is what allows us to do things like play a musical instrument, ride a bicycle, or add up a bill. Sleep scientists think these two types of memory are influenced by different parts of the sleep cycle, but there is a consistent pattern: Learn something new during the day, consolidate what you have learned during a good night's sleep, then remember or perform the task better in the morning.

For decades, scientists have identified stages of sleep by measuring electrical activity through the scalp with the electrodes of an electroencephalogram (EEG). The two main kinds of sleep are rapid eye movement (REM) and non-REM (NREM). NREM is further divided into four stages, from shallow to deep (stages 1 to 4). The two deepest stages (3 and 4) are also called slow wave sleep (SWS) because the wave forms on the EEG occur at the lowest frequency. REM sleep alternates regularly with NREM, in a cycle completed about every 90 minutes. Early in the night, NREM dominates, but toward morning, REM sleep takes up larger proportions of the 90 minute cycle. We dream most vividly during REM sleep — and the most vivid dreams of all occur at the end of the night. In general, NREM sleep facilitates declarative memories, and REM sleep, procedural memories, but the distinction is not clear-cut.

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