Sleep: everybody needs it, nobody gets enough of it, and college students dream about it. According to Merriam-Webster Dictionary, sleep is defined as “the natural periodic suspension of consciousness during which the powers of the body are restored”. Sleep is on everyone’s mind but very little is known about the details of neural processes during sleep. In the past, sleep was believed to be the process of rest in all bodily functions, but within the last 50 years sleep has been proven to be critical for memory integration.
Dr. Ken Pallar from the Psychology Department of Northwestern University recently spoke at Loyola University about his research with targeted memory reactivation (TMR) and its positive effect on learning and memory. Dr. Pallar ran a study in which TMR was utilized in the form of auditory cues. Volunteers were taught two melodies and then asked to sleep, with one of the melodies playing softly throughout. After the nap, the volunteers were asked to play the melodies. The results showed a considerable improvement of performance for the melody played during sleep. This further illustrates Dr. Pallar’s argument that memory consolidation improves with repetition and rehearsal and is advanced even further still when revisited during sleep.
Dr. Pallar also argues that, contrary to previous beliefs, memory consolidation and construction of new neural networks are most successful during slow-wave sleep as opposed to REM sleep. The auditory TMR in the study above was executed during these slow-wave sleep cycles which produced such definitive results. This is due to the fact that the slow oscillations during slow-wave sleep have high-amplitudinal and synchronized EEG activity.
If we can agree that slow-wave sleep is directly related to memory consolidation and integration, then what about those that struggle to achieve optimal slow-wave event rates in their sleep? For example, it has been proven that people who suffer from obstructive sleep apnea (OSA) achieve reduced event rates in slow-wave sleep. An article published in the Journal of Clinical Sleep Medicine titled “Marked Reduction in Obstructive Sleep Apnea Severity in Slow Wave Sleep” examines this complex dynamic. In short, the researchers found that this relationship occurred in a vicious cycle. Those who suffer from sleep apnea achieve slow-wave sleep less often, but when they do, slow-wave sleep has been proven to help reduce the effects of sleep apnea such as disordered breathing and arousal.
Clearly, slow-wave sleep is beneficial for a plethora of reasons but how do we ensure these slow-wave sleep event rates in people who deal with sleeping disorders? And are these disorders indirectly impacting these people’s ability to filter and consolidate memories?
For more info on this sleep apnea study, click here.
http://jcsm.aasm.org/Articles/05_06_519.pdf
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