Everyone seems to know that sleep is important in order to live a healthy life, however approximately 30 percent of American adults sleep less than 6 hours a night according to the CDC. College students tend to be one of the most sleep deprived populations. This sleeplessness negatively impacts students grades and work performance; one seemingly obvious reason for this is the lack of focus when a student is tired. A second reason for the grade impact is that sleeping solidifies learning and memory. Humans remember information through a few processes. One of those processes is called acquisition, this simplified as gaining new information, like in classes. Another of the processes is consolidation, this happens during sleep. When people are asleep the synapses in the brain strengthen, which allows for better and faster recall. When a lack of sleep occurs consolidation decreases.
One study published in 2007 demonstrates consolidation by using people that have learned something in a lab, then while the participants were sleeping they allowed them to smell a scent that had been present during their learning in the lab. The results showed that when the scent was presented during slow wave sleeping it "improved the retention of hippocampus-dependent declarative memories but not of hippocampus-independent procedural memories." Dependent declarative memories are conscious and long term, within this group there are subgroups within this memory which include; episodic which is for personal experiences, and semantic memory, which stores learned facts. While independent procedural memories are long term as well, this is primarily for tasks that are unconscious, this can include things like typing on a key board. While procedural did not reap any benefits of sleep paired with scent, dependent memory certainly did. Slow wave sleeping is the the deepest stage of non-rem sleep, Slow wave sleep, or SWS is shown with modern of technology as having a high amount of brainwave activity, ironically in this stage the brain seems to be less responsive to external stimuli. Another finding in this study was that scent "re-exposure was ineffective during rapid eye movement sleep or wakefulness or when the odor had been omitted during prior learning". Rapid-eye movement (REM) has more consciousness to the environment than SWS. I find this study interesting because it illustrates the complexity of a few of the stages of sleep; as well as the influence the environment can have on one's sleep. During REM sleep the body is essentially paralyzed in the muscles, this is what prevents people from acting out their dreams. Some people's muscle systems fail to be paralyzed during this stage of sleep. REM sleep is also accompanied by vivid dreams and high cortical activity.
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Sleep is a very complex subject that can't be fully explained by science at this point in time. This article just touches the surface of some of the science involved in sleep and memory.
