The Role of Sleep in Learning and Memory.
Students tend to overload themselves by overnight study to memorize all the study material. However, most of them do not realize that we will have a better result by an adequate sleep than having a three hour sleep before an exam to memorize all the material. This restless lifestyle will significantly reduce health level and in fact reduces our memory consolidation and opportunity to use our unconscious mind to improve the skill that we learn.
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This theory was first introduced by Muller and Pilzecker about 100 years ago.
They made a hypothesis that memory consolidation is time dependent and require regulating from our brain cell which leads to further development in memory consolidation theory nowadays. (McGaugn, 2000. ) According to “Neurology board review: An illustrated study guide. ” written by Professor Mowzoon, sleep is divided into 2 main types, which is non-rapid eye movement (NREM) and rapid eye movement (REM). NREM sleep occur seventy five percent of our sleep and REM sleep only occur for twenty five percent of our sleep. NREM sleep can divide into 4 stages. Stage 1 happens when we are between being awake and asleep.
Stage 2 occurs at the beginning of sleep; brain will produce periodic brain wave activity known as sleep spindles that can relax our body muscle and heart rate. Stage 3 and 4 take place in deep sleep. In these stages, our body tissue cultivates and repairs. Lastly, stage 5 of the sleep is involved in REM sleep where most dreaming occurs. In REM sleep, brain and other parts of our body becomes more active but muscles remain in a lessen state. (Mowzoon, 2007) A journal article “Sleep dependent memory consolidation” from Nature precisely categorizes sleep stages and memory.
There are several type of memories but commonly they are divided into declarative memories which we can recall in our mind and non-declarative memory where normally used without conscious. The term memory consolidation is referring to memory stabilization, where memories become more resistible to interference. Several studies show that certain memories are consolidation through REM sleep as complex cognitive procedural learning take place. Procedural memory and spatial memory are greatly improved in REM sleep, where both these memories help to recording information and how to get things done.
Motor skills like dancing, would advance while we are in REM sleep. Positron emission tomography (PET) brain imaging has demonstrated that the night after training, region that is active during task performance is reactivated during REM sleep. Besides, even event related potentials shows that high temporal resolution of brain processing in the period of REM sleep. (Stickgold, 2005)The result shows that REM sleep and memory consolidation are highly positive correlated, as a REM-rich periods person will be 3 times more likely to improve in certain skill than a sleep deprivation person.
Endogenously, Nature NeuroScience did an electrophysiological reading between hippocampus and neocortex respond to episodic and semantic memories. Episodic memory is memories that involve emotion, while semantic memory refers to factual information and knowledge. Both of these memories are categorized in declaration memory. In the experiment, a group of people were given some task and simulating the learning multiple times. After that, subjects are given 2 detail fMRI scan that one is scheduled directly after the learning session and another scan 48hours later.
The result shows that there is an increase in functional connectivity over time between hippocampus and medical prefrontal cortex in the first scan is lower than second scan. Subject remember more detailed and perform better after a good night sleep. Therefore learning is highly influence by the successively of reactivation between hippocampal and prefrontal network during our sleeping cycle. (Peyrache, 2009) In addition, the journal of Science written by Maquet, show that sleep has been occupied that plastic cerebral change due to fresh memory and learning.
The recurrence of neuronal bonds during sleep is proven by a few experiments. The neural activity is further shown in walking behavior seems to be reestablished during sleep. The reactivation will increase the intercellular connection strength between the element of network and incorporation of the new experience into long term memory. (Maquet, 2001) Both of this experiment proven that REM sleep has great effect to memory consolidation and learning. Exogenously, sleep is also illustrated to be obliging in memory consolidation and learning.
Practice is not the only way to attainment all skill, performance could be improve between learning period and not within it. Explicit skill where we learn it intentionally is sleep-dependent. From an experiment from journal of Current Biology, offline skill improvement can only observed within 12 hours including sleep. The result show that implicit skill might improve due to time but explicit skill is positive correlated to sleep. When we are fully conscious of learning a new thing, the improvement of skill without practice is totally reliant on sleep. Robertson, 2004) Moreover, BBC news reported that in United Kingdom, a group of adult was given a task and for the group who were sent to sleep did better than those who carried on without sleep. Dr Matthew Walker mentions that “Sleep not only rights the wrong of prolonged wakefulness, but at neurocognitive level, it moves you beyond where you were before you took a nap”. This supplementary enhances the theory that, sleep will improve memory consolidation and learning. (BBC, 2010)
As a college student, I fully understand that weighty academic course loads leads to sleep deprivation, but a good sleeping cycle will helps to boost up our academic result. Even though sleep helps to improve our academic, we still have to put in the same effort in our daily life to maintain and improve our result.
References: Mowzoon, N. , M. D. , Flemming, K. , D. (2007). Neurology board review: An illustrated study guide. Rochester, MN: Mayo Foundation for Medical Education and Research. Stickgold, R. (2005). Sleep-dependent memory consolidation. Nature, 437(7063), 1272-1278. Peyrache, A. , Khamassi, M. , Benchenane, K. , Wiener, S. , I. , Battaglia, F. , P. (2009). “Reply of rule-learning related neural patterns in the prefrontal cortex during sleep. ” Nature NeuroScience, 12(7), 919-926. Doi:10. 1038/nn. 2337 Maquet, P. (2001) The role of sleep in learning and memory. Science, 294(5544), 1048-1052. DOI: 10. 1126/science. 1062856 McGaugh, J. , L. (2000). Memory – A century of consolidation. Science, 287(5451), 248-251. DOI:10. 1126/science. 287. 5451. 248 “Nap ‘boosts’ brain learning power. BBC News 21 February 2010. Retrieved from: http://news. bbc. co. uk/2/hi/health/8524549. stm. Robertson, E. M. ; Pascual-Leone, A. ; Press, D. Z. (2004). “Awareness modifies the skill-learning benefits of sleep”. Current Biology. 14(3): 208–212. DOI:10. 1016/j. cub. 2004. 01. 027 Wamsley, E. , J. , Tucker, M. , Payne, J. D. , Benavides, J. , A. , & Stickgold, R. (2010). Dreaming of a learning task I associated with enhanced sleep dependent memory consolidation. Current Biology, 20(9), 850-855. DOI: 10. 1016/j. cub. 2010. 03. 027