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
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