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.

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.

People who enjoy a dream-filled sleep are significantly better at recalling information and making links between facts when they wake, scientists found.

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.

Scientists have been working on connections between sleep, dreams and brain activity since the REM state was first identified in 1953 by US researchers.

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.

They found that people woken while their closed eyes made jerking movements recalled much more colorful and elaborate dreams than people woken during other stages of sleep.

This process may take place as memories are shifted from one part of the brain to others.