Arzi A., Shedlesky L., Ben-Shaul M., et al. (2012). Humans can learn new information during sleep. Nature Neuroscience, 15:1460-1465 Details
Customer study highlights
Certainly, emotional and cognitive centers in the brain remain active during sleep. One consequence of this activity is that sensory stimuli are constantly appraised and can potentially be used to trigger an internal 'alarm' causing us wake up - should threatening sounds or physical sensations be heard or felt.
This ability is possibly a remnant of early postnatal cognitive development. Newborn babies, for instance, are capable of simple associative, or paired, learning while asleep which is consistent with the notion of a ‘blank’ and highly active mind processing a sudden barrage of new sensory information. Adult brains are rather the opposite and are somewhat resistant to this process – leading some researchers to question whether the sleeping adult brain is capable of learning at all. A recent Nature Neuroscience publication shows that it is - but there was a catch: the subjects weren’t aware of the learning process.
In a study partly undertaken at the Weizmann Institute of Science, associative learning was tested in sleeping adults using specific sounds paired with either pleasant (shampoo or deodorant) or offensive (rotten fish or carrion) odors during sleep. Using standard polysomnography (EEG, EMG, nasal airflow and oximetry - recorded using a PowerLab, an Octal Bio Amp and ML141 spirometer), the researchers showed that - while asleep - pleasant odors triggered a deeper sniff, while offensive odors triggered shallow breathing. Later that night, researchers played the tones alone, and showed that sniff volume was larger after a tone that was previously paired with a pleasant odor, indicating participants had learned the association while asleep. The next day, during waking, response to tones that were previously paired with pleasant odors (during sleep) also triggered larger sniff volumes, indicating a subconscious retention effect.
The next step? Utilizing this to become smarter; perhaps a third smarter since this is approximately how much time we spend sleeping.