Learn new vocabulary during deep sleep

Sleeping is sometimes considered an unproductive period. Could sleeping time be used more productively, for example to learn a new language? To date, sleep research has focused on stabilizing and consolidating memories formed during the previous day. However, learning during sleep has rarely been examined. There is ample evidence of a recurring recapitulation in the dormant brain of information learned upon waking. Replay during sleep strengthens still fragile memory traces and integrates newly acquired information into the pre-existing knowledge stock.

If replay during sleep improves the storage of information learned upon waking, initial processing of new information should also be feasible during sleep, possibly creating a memory trace that lasts until the waking state. This was the research question of Katharina Henke, Marc Züst and Simon Ruch from the University of Bern, Switzerland. These investigators show for the first time that new foreign words and their translations could be badociated during a midday nap to badociations stored in the waking state. After waking up, participants could reactivate the badociations formed by sleep to access the meaning of words when they were represented with foreign words previously played during sleep. The hippocampus, a brain structure essential to badociative wakefulness learning, has also helped recover trained sleep badociations. The results of this experiment are published in open access in the scientific journal Current biology.

The research group examined whether a sleeping person was able to form new semantic badociations between foreign words played and words of translation during the active states of brain cells, called "higher states". When we reach deep sleep stages, our brain cells progressively coordinate their activity. During deep sleep, brain cells are usually active for a brief period before entering jointly into a state of brief inactivity. The active state is called active state and inactive state, state disabled. The two states alternate every half second or so.

Semantic badociations between the words of an artificial language played in sleep and their translations into German, these were only coded and stored if the second word of a couple was played over and over ( two, three or four times) during playback. For example, when a sleeping person heard the pairs of words "tofer = key" and "guga = elephant", she was then able, after waking, to categorize with greater accuracy than chance if the foreign words played in sleep were of great significance Guga ") or small (" Tofer ")." It was interesting that the linguistic areas of the brain and the hippocampus – the hub of memory of the brain – were activated at during the extraction of vocabulary learned during sleep, because these brain structures normally facilitate the learning of new vocabulary, "-author of paper." These brain structures seem to play a mediating role in the formation of memory , regardless of the state of dominant consciousness – unconscious during deep sleep, conscious during waking. "

In addition to its practical relevance, these new data on sleep learning challenge current theories of sleep and memory. The notion of sleep as an encapsulated mental state into which we are detached from the physical environment is no longer tenable. "We could refute the idea that sophisticated learning is impossible during a deep sleep," says co-author Simon Ruch. The current results highlight a new theoretical notion of the relationship between memory and consciousness, published by Katharina Henke in 2010 (Neuroscience Nature Advisory). "To what extent and with what consequences deep sleep can be used to acquire new information will be the focus of research in the coming years," said Katharina Henke.

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University of Bern