To remember new information - for example, a telephone number or a word in a different language is one thing, while it's another to create a specific archive in the brain, that is always accessible when you have need of it.
Analysis, led by researchers at Harvard Medical School, proved that sleep aided the absorption of new information, as well as the creation of a new archive in the brain.
The scientists discovered that sleep helps us to remember new words and to enrich our vocabulary. During a long experiment, the researchers made volunteers learn new words at night and then immediately tested them.
The volunteers slept in the lab the whole night, while during their sleep their brain activity was recorded using electroencephalography.
In the morning, it became clear that the volunteers in the experiment were able to recall the new words much faster after waking up than immediately after hearing them for the first time.
This phenomenon was not encountered in a group of volunteers who were lectured early in the morning and given a test late at night, without having any opportunity to sleep.
Study of the brain waves of the volunteers during sleep showed that deep sleep, much more than REM sleep or light sleep, helped in taking in new information.
The researchers found various types of activity in the sleeping brain. The periods of sleep are short, but the intense outbursts of brain activity, showed the exchange of information between different areas of memory in the brain - the hippocampus deep in the brain and the neocortex.
Memory in the hippocampus is loaded separately by the other types of memory, while the memory in the neocortex is related to other types of knowledge. The volunteers who slept more hours were successful in their tests of the new words, which proved that the new words were transferred from the hippocampus to the neocortex during sleep.
Prof. Gareth Gaskell, who headed the study announced, "The results of the tests showed the importance of sleep and the main process of vocabulary expansion in the brain. It is likely that the brain reacts to other methods of learning in the same way."