let's talk about the stages of sleep this diagram shows the stages of sleep the first four stages of sleep are non-rem the first non-rem cycle takes around 60 to 90 minutes for completion stages 3 and 4 of non-rem sleep are also known as slow wave sleep because of the low frequency of brain waves shown on the electroencephalogram or eeg during these stages the phenomenon known as sleep walking or somnambulance occurs during the slow wave stages of non-rem sleep it is also thought that consolidation of declarative memories from short-term to long-term occurs during the slow wave non-rem stages before the first rem cycle during the night the individual goes in the reverse order back through the non-rem stages the first rem stage lasts for about 10 minutes and the subsequent rem stages that come later in the night increase in length and maybe even up to one hour in duration during rem cycles skeletal muscles are paralyzed except for those for eyeball movement and the diaphragm for breathing however the brain is very active and for this reason rem is sometimes referred to as paradoxical sleep rem is characterized by rapid eye movement increased autonomic activity and dreaming consolidation of procedural memories also occurs during rem through the night the sleeping individual alternates between ram and non-rem stages with progressively longer ram stages and less deep slow wave non-rem sleep occurring later in the night a sleep study also called polysomnography may be performed to help in the diagnosis of sleep disorders polysomnography monitors brain waves blood oxygen levels breathing and heart rate and eye and leg movements sleep disorders that polysomnography may help diagnose include narcolepsy characterized by sudden bouts of sleepiness during the day called sleep attacks also sleep apnea where breathing stops and starts while sleeping and rem sleep behavior disorder where individuals act out their dreams while they sleep a sleep study may be performed for unusual behaviors during sleep like sleepwalking moving around excessively or rhythmic movements also for a condition called periodic limb movement disorder where patients unknowingly extend and flex their legs during sleep which may be associated with restless leg syndrome additionally a sleep study may be performed for unexplained chronic insomnia where an individual has trouble staying or falling asleep now for six questions please pause the video and think of your answers if you answered the following you are correct if you answered the following you are correct again thanks for watching