So far, it has been a known fact that learnt knowledge solidifies during sleep. But, it has been not quite clear how this is working. In a study, neuroscientists of the University of Lübeck, Germany, and the University Hospital investigated memory formation during sleep. In the study it was determined that an unconscious reactivation of the memory during deep sleep enhances memory formation. During sleep, the scientists tried to arouse associations with the help of a scent of roses to things they have learned during the day with the same scent. Actually, there could be reached a better saving and enhanced memory post-sleep.
Scents are suitable for these investigations because they have the special feature to induce memories and to nearly have no negative effect on sleep.
In the study, 18 healthy test subjects had to learn the position of 15 pairs of images on a computer screen. While doing so, the room was filled with the scent of roses. After learning the position of the pairs the probands had to go to bed. During sleep, they were offered the scent of roses. And, the following night they were offered an odorless carrier substance.
After stimulation during deep sleep with the scent of roses the participants significantly remembered more pairs (97 percent) than after the night without any scent of roses (86 percent). During sleep, the scent of roses was linked to the learned content of the memory game and therewith was decisive for the enhanced memory formation. Stimulation with the scent of roses during REM-sleep or during waking state had no enhanced effect on memory formation.
Based on MRI of the brain, an enhanced activity of the hippocampus could be determined when the sleeping test persons were presented with the scent of roses. The sense of smell is linked with the hippocampus more directly than our eyes and ears – and this might be an explanation for the effect observed.
The findings are related to reminiscence on facts and events that are processed on the hippocampus – like the position of the pairs of images – and that are specially activated during deep sleep. The learning of motoric-procedural tasks like typing of a finger-sequence do not depend on the hippocampus. They could not be influenced with the scent. Maybe because it is hard to link odors with motoric features.
This post is also available in / Diesen Beitrag gibt es auch in: German
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