Sleep-learning

Sleep-learning (also known as hypnopædia, or hypnopedia) is an attempt to convey information to a sleeping person, typically by playing a sound recording to them while they sleep. Although often used in pop culture as a way to introduce new information (see 'In Fiction'), sleep is considered an important period for memory consolidation. Sleep-learning (also known as hypnopædia, or hypnopedia) is an attempt to convey information to a sleeping person, typically by playing a sound recording to them while they sleep. Although often used in pop culture as a way to introduce new information (see 'In Fiction'), sleep is considered an important period for memory consolidation. Although learning new information during sleep has not been considered possible, at least to the extent it is used in fiction, the term hypnopedia has also been used to refer to the technique of playing sounds or odors during sleep in order to boost memory for previously learned information. Hypnopedia, in this sense, is related to a technique now known as Targeted Memory Reactivation (TMR). Unlike the pop-culture idea of sleep-learning, or learning new information during sleep, TMR pairs newly acquired information with sounds that can later be played, or cued, during electroencephalography (EEG) verified sleep to strengthen memory. This type of sleep reactivation in humans has been found successful in strengthening memory in a number of different paradigms including language learning, motor-skill learning, and spatial memory. Research in TMR has shown that cueing sounds that are associated with previously learned material over a period of sleep is more beneficial to memory than a similar period of wake. Likewise, cued material is also better preserved than material that is not cued during sleep. In 1927, Alois Benjamin Saliger invented the Psycho-Phone for sleep learning, stating that 'It has been proven that natural sleep is identical with hypnotic sleep and that during natural sleep the unconscious mind is most receptive to suggestions.' Since the electroencephalography studies by Charles W. Simon and William H. Emmons in 1956, learning by sleep has not been taken seriously. The researchers concluded that learning during sleep was 'impractical and probably impossible'. They reported that stimulus material presented during sleep was not recalled later when the subject awoke unless alpha wave activity occurred at the same time the stimulus material was given. The idea of reactivating memories in humans to improve memory began with the finding that neurons active in the hippocampus in rodents were found to fire together during subsequent sleep. In 2012, research from the Weizmann Institute of Science indicated that classical conditioning can occur during sleep by using odor recognition. 'During sleep, humans can strengthen previously acquired memories, but whether they can acquire entirely new information remains unknown. The nonverbal nature of the olfactory sniff response, in which pleasant odors drive stronger sniffs and unpleasant odors drive weaker sniffs, allowed us to test learning in humans during sleep.' The idea of sleep-learning is found in influential science fiction and other literature. The following examples are listed chronologically by publication or original air date, when known.