August 14, 2006 – Data from a recent clinical trial1 indicate that sleep improves the ability to properly retain memorized facts, data and other details. Sleeping after memorizing something would allow memory to better consolidate memories and learning, according to researchers at the Center for Sleep and Cognition, Harvard School of Medicine.
The researchers were interested in a specific form of long-term memory, the so-called “explicit” or “declarative” memory, that which makes it possible to remember factual details and to keep a precise and intact memory of them.
We already knew that sleep could help the brain consolidate learning related to “implicit” or “non-declarative” memory such as riding a bicycle, juggling, tying shoelaces, acquiring specific know-how, etc. The Harvard University team has just demonstrated that the same is true for “explicit” memory, that which allows to store in long-term memory facts, events, images or propositions.
The 60 subjects participating in the study (33 women and 27 men) ranged from 18 to 39 years old. Each had to memorize 20 pairs of randomly associated words and take a memory test after 12 hours. Some had the opportunity to sleep between the learning session and the test. The others simply went about their normal activities while awake.
When taking the memory test, part of the subjects had to learn a new set of 20 pairs of words in order to create “mnemonic interference” with the words memorized 12 hours earlier. This type of interference has the effect of confusing the subject who tends to forget the previously memorized data and replace them with the new ones.
The results indicate that people who slept between the learning session and the test had better memory of the sequence of memorized words. What’s more, their memory was more resistant to interference when comparing their results to those of people who hadn’t had a chance to sleep.
The researchers explain that, during sleep, the brain “revises” the learning memorized during the previous hours. Associated with increased activity of the hippocampus – the part of the brain responsible for storing memories – this reverberation of information would have the effect of strengthening memories and making them less vulnerable to interference.
Pierre Lefrançois – PasseportSanté.net
According to HealthDay News.
1. Ellenbogen JM, Hulbert JC, Stickgold R, Dinges DF, Thompson-Schill SL. Interfering with theories of sleep and memory: sleep, declarative memory, and associative interference, Curr Biol., 2006 Jul 11; 16 (13): 1290-4.
