if the already learned information is re-played during deep sleep. This is possible because the brain can re-process the information over-and-over again to consolidate the memory. However, it is not known if the brain can process new information that is input during sleep, such as learning new words and recalling them after waking.
It is hypothesized that if re-playing learned information during sleep
can facilitate the brain to consolidate memory; it could also be possible for the brain to learn new information played for the first time during sleep. In fact, this hypothesis has been proved by the unprecedented findings of this study.
The study was led by Dr. Katharina Henke, PhD, who is a Professor of Experimental Psychology and Neuropsychology at the Institute of Psychology, University of Bern, Switzerland. The study was carried out by Dr. Marc Züst, PhD and Dr. Simon Ruch, PhD, who are postdocs in Professor Henke's lab.
The study has been published in the journal Current Biology
, a Cell Press publication.
Key Aspects of the Study
The primary aspects that were investigated pertain to brain activity and its role in language processing. These are briefly highlighted below: Brain Activity:
- Brain activity fluctuates between active states ("Up-states") and inactive states ("Down-states") during deep sleep
- Duration of active ("Up") and inactive ("Down") states lasts for half-a-second each
- Semantic associations between foreign words and translated words during deep sleep were evaluated
- The foreign and translated word-pairs were encoded and stored in the memory only if the second word of a pair was repeated 2-4 times during the "Up-state" phase of brain activity
- For example, foreign word-pairs "tofer" (key) or "guga" (elephant) played during deep sleep were accurately interpreted as "something small" (tofer) or "something big" (guga) after waking
- This study demonstrates for the first time that foreign words and translated words can be associated during sleep and the associations can last until waking
In this regard, Züst says: "It was interesting that language areas of the brain and the hippocampus - the brain's essential memory hub - were activated during the wake retrieval of sleep-learned vocabulary because these brain structures normally mediate wake learning of new vocabulary."
He adds: "These brain structures appear to mediate memory formation independently of the prevailing state of consciousness - unconscious during deep sleep, conscious during wakefulness."
The evidence arising from the current study suggests that the existing theories on sleep and memory could be seriously challenged and may require a thorough revision in the light of the new findings. The present understanding that sleep is a state of mental detachment from the physical world, may no longer be justifiable. Importantly, the findings indicate a paradigm shift in our theoretical understanding of memory
and consciousness and their interrelationship. "We could disprove that sophisticated learning is impossible during deep sleep",
Henke concludes: "In how far and with what consequences deep sleep can be utilized for the acquisition of new information will be a topic of research in upcoming years."
The study was funded by the University of Bern, Switzerland. Reference :
- Implicit Vocabulary Learning During Sleep is Bound to Slow-Wave Peaks - (https://doi.org/10.1016/j.cub.2018.12.038)