People can learn new information during sleep: Study

u00a0 This indicates that people can learn new information while they sleep and this can unconsciously modify their waking behaviour u00a0 Sleeplearning experiments are notoriously difficult to conduct For one thing one must be sure that the subjects are actually asleep and stay that way during the ldquolessonsrdquo u00a0 The most rigorous trials of verbal sleep learning have failed to show any new knowledge taking root While more and more research has demonstrated the importance of sleep for learning and memory consolidation none had managed to show actual learning of new information taking place in an adult brain during sleep u00a0 Representational picture Prof Noam Sobel and research student Anat Arzi together with Sobelrsquos group in the Institutersquos Neurobiology Department in collaboration with researchers from Loewenstein Hospital and the Academic College of Tel Aviv ndash Jaffa chose to experiment with a type of conditioning that involves exposing subjects to a tone followed by an odour so that they soon exhibit a similar response to the tone as they would to the odour u00a0 The pairing of tones and odours presented several advantages Neither wakes the sleeper in fact certain odours can promote sound sleep yet the brain processes them and even reacts during slumber Moreover the sense of smell holds a unique nonverbal measure that can be observed ndash namely sniffing u00a0 The researchers found that in the case of smelling the sleeping brain acts much as it does when awake We inhale deeply when we smell a pleasant aroma but stop our inhalation short when assaulted by a bad smell This variation in sniffing could be recorded whether the subjects were asleep or awake Finally this type of conditioning while it may appear to be quite simple is associated with some higher brain areas ndash including the hippocampus which is involved in memory formation u00a0 In the experiments the subjects slept in a special lab while their sleep state was continuously monitored As they slept a tone was played followed by an odour ndash either pleasant or unpleasant Then another tone was played followed by an odour at the opposite end of the pleasantness scale Over the course of the night the associations were partially reinforced so that the subject was exposed to just the tones as well The sleeping volunteers reacted to the tones alone as if the associated odour were still present ndash by either sniffing deeply or taking shallow breaths u00a0 The next day the now awake subjects again heard the tones alone ndash with no accompanying odour Although they had no conscious recollection of listening to them during the night their breathing patterns told a different story When exposed to tones that had been paired with pleasant odours they sniffed deeply while the second tones ndash those associated with bad smells ndash provoked short shallow sniffs u00a0 The team then asked whether this type of learning is tied to a particular phase of sleep In a second experiment they divided the sleep cycles into rapid eye movement REM and nonREM sleep and then induced the conditioning during only one phase or the other u00a0 Surprisingly they found that the learned response was more pronounced during the REM phase but the transfer of the association from sleep to waking was evident only when learning took place during the nonREM phase u00a0 u00a0Sobel and Arzi suggest that during REM sleep we may be more open to influence from the stimuli in our surroundings but socalled ldquodream amnesiardquo ndash which makes us forget most of our dreams ndash may operate on any conditioning occurring in that stage of sleep In contrast nonREM sleep is the phase that is important for memory consolidation so it might also play a role in this form of sleeplearning u00a0 Although Sobelrsquos lab studies the sense of smell Arzi intends to continue investigating brain processing in altered states of consciousness such as sleep and coma u00a0 ldquoNow that we know that some kind of sleep learning is possible we want to find where the limits lie ndash what information can be learned during sleep and what information cannotrdquo said Arzi u00a0