[揽瓜阁精读] 24. Rapid Eye Movement.

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1st:  REM sleep is best known as the period that intense dreams occur in human. According to EEG result, REM sleep shows high frequency and low amplitude waves, showing similar with waking status. Besides that, activities in neurological subunits of the brain similar in awakened state. " theta rhythm" has the similar result. And even the brain temperature shows similarity.
2nd: recently, accidental discovery augmented our understanding. Scientists originally thought PGO spikes only active in REM sleep, but a laboratory accident found out both sounds and touch could easily produce PGO spikes
3rd: the similar result in EMPs, hence PGO spikes and EMPs are now seen as varieties of a general alerting response.