There is evidence to show that sleeping brain is capable of processing sensory information. Presentation of meaningful stimuli, such as one’s own name, during sleep elicits different brain responses than presentation of meaningless names or tones. An odor presented during the acquisition of a memory while awake, if later presented during sleep, resulted in enhanced recall at ensuing wake. Hippocampal-independent learning that does not require awareness has been observed in sleeping rats, infants, and during drug-induced or slow-wave sleep (SWS) in humans.In none of these studies did externally presented stimuli actually lead to learning new things during sleep.
Can we actually learn entirely new information during sleep?
Arzi and colleagues ( Israel) used differential partial reinforcement trace conditioning between tones and odors during sleep.They used the sniff response (an odorant specific change in nasal airflow in which pleasant odors drive stronger sniffs and unpleasant odors drive weaker sniffs) as the nonverbal implicit measure of processing. During wake, the sniff response can be conditioned to a tone, such that different tones then drive different sniffs.They paired different tones with pleasant and unpleasant odors during sleep and then tested whether these tones alone, without an ensuing odor, would induce stronger or weaker sniffs in accordance with the odor pleasantness with which they were previously associated. They tested for such learned tone-induced sniffs during the same night’s sleep and in ensuing wake.
Sniff volume during sleep was larger after a tone that was previously paired during sleep with a pleasant odor than after a tone that was previously paired during sleep with an unpleasant odor.
Participants learned a novel association and acted on this learning, all during sleep.
Learning persisted in both sleep stages, yet the learned tone-specific sniff response was more pronounced during REM.
Novel information learned during NREM alone was retained in ensuing wake, but information learned during REM alone was not.
Learning occurred without later awareness of the learning process.
It is already established that sleeping brain can perform sophisticated memory processing. The present study shows that human brain can learn new information during sleep.However, it does not mean that complex forms of learning can occur during sleep.
Summary of the article:
Humans can learn new information during sleep. Arzi A, Shedlesky L, Ben-Shaul M, Nasser K, Oksenberg A, Hairston IS, Sobel N.Nat Neurosci. 2012 Oct;15(10):1460-5