People who enjoy a dream-filled sleep are significantly better at recalling information and making links between facts when they wake, scientists found.
But recharging with a shallow nap offers no such mental boost, the research suggests.
The results of the study add to the growing body of evidence that Rapid Eye Movement (REM) sleep is crucial to the brain’s ability to lay down and consolidate memories.
An average night’s repose includes four or five spells of REM sleep, but these bursts tend to be lengthier towards the end of the night.
This means that adults who get less than the recommended seven to eight hours a night – and therefore insufficient REM sleep – may be damaging their mind’s ability to form strong memories.
Although REM sleep is not classified as a type of deep sleep, it is only reached after the brain has passed through deep sleep stages.
For the most recent study, participants were shown groups of three words – such as “cookie”, “heart” and “sixteen” – and asked to find another word that can be associated with all three words.
In this example, the answer would have been "sweet”. 外语教育￥网www.for68.com
Participants were tested once in the morning and then given the same task again in the afternoon. In between, some were allowed a nap with REM sleep, some a nap without REM sleep, while the others had a quiet rest period.
The quiet rest and non-REM sleep groups showed no improvement in their test results, but the REM sleep proup improved on their morning performance by an average of almost 40 per cent.
Dr Sara Mednick, a sleep researcher at the University of California in San Diego who led the study, believes that the formation of connections between previously unassociated information in the brain – which leads to creative problem-solving – is encouraged by neurological changes which occur during REM sleep.
Scientists have been working on connections between sleep, dreams and brain activity since the REM state was first identified in 1953 by US researchers.
They found that people woken while their closed eyes made jerking movements recalled much more colourful and elaborate dreams than people woken during other stages of sleep.
It is now believed that sleep acts as a sort of mental filing system, enabling the brain to sort relevant information that needs to be retained from useless information which can be discarded. This process take place as memories are shifted from one part of the brain to others.