Behavioral Correlates of Sleep States and Stages Polysomnographic staging of sleep correlates with behavioral changes during specific states and stages. During the transitional state between wakefulness and sleep (stage 1 sleep), subjects may respond to faint auditory or visual signals without "awakening." Memory incorporation is inhibited at the onset of NREM stage 1 sleep, which may explain why individuals aroused from that transitional sleep stage frequently deny having been asleep. Such transitions may intrude upon behavioral wakefulness after sleep deprivation, notwithstanding attempts to remain continuously awake (see "ShiftWork Disorder," below). Awakenings from REM sleep are associated with recall of vivid dream imagery 80%. | Chapter 028. Sleep Disorders Part 4 Behavioral Correlates of Sleep States and Stages Polysomnographie staging of sleep correlates with behavioral changes during specific states and stages. During the transitional state between wakefulness and sleep stage 1 sleep subjects may respond to faint auditory or visual signals without awakening. Memory incorporation is inhibited at the onset of NREM stage 1 sleep which may explain why individuals aroused from that transitional sleep stage frequently deny having been asleep. Such transitions may intrude upon behavioral wakefulness after sleep deprivation notwithstanding attempts to remain continuously awake see Shift- Work Disorder below . Awakenings from REM sleep are associated with recall of vivid dream imagery 80 of the time. The reliability of dream recall increases with REM sleep episodes occurring later in the night. Imagery may also be reported after NREM sleep interruptions though these typically lack the detail and vividness of REM sleep dreams. The incidence of NREM sleep dream recall can be increased by selective REM sleep deprivation suggesting that REM sleep and dreaming per se are not inexorably linked. Physiologic Correlates of Sleep States and Stages All major physiologic systems are influenced by sleep. Changes in cardiovascular function include a decrease in blood pressure and heart rate during NREM and particularly during slow-wave sleep. During REM sleep phasic activity bursts of eye movements is associated with variability in both blood pressure and heart rate mediated principally by the vagus. Cardiac dysrhythmias may occur selectively during REM sleep. Respiratory function also changes. In comparison to relaxed wakefulness respiratory rate becomes more regular during NREM sleep especially slow-wave sleep and tonic REM sleep and becomes very irregular during phasic REM sleep. Minute ventilation decreases in NREM sleep out of proportion to the decrease in metabolic rate at sleep onset resulting in a .
