Awake/NREM-sleep/REM-sleep cycle has different properties at each stage {AIM model}. Sleep-cycle stages have different Activation levels, Input and output, and neurotransmitter Modulation.
activation
Activation is from pons reticular activating system and has pathways to nearby brainstem areas, thalamus, and spinal cord. Awakeness and REM sleep have high-frequency low-amplitude EEG waves. NREM sleep has low-frequency high-amplitude EEG waves. Stage II NREM sleep has distinctive sleep-spindle EEG.
Cortical regions differ in activation cycles, input, output, and modulation. Hypothalamus superchiasmatic nucleus starts NREM sleep and controls progress through NREM sleep. REM sleep activation goes from pons to lateral geniculate to occipital (PGO). Reticular formation blocks spinal-cord sense and motor activity during REM sleep [Hobson, 1989] [Hobson, 1994] [Hobson, 1999] [Hobson, 1999] [Hobson, 2002] [Hobson et al., 1998].
input and output
Reticular activating system neurons can inhibit afferent axons from senses and efferent axons to muscles. For awakeness, input comes from outside, and output goes to muscles. For NREM and REM sleep, inputs only come from inside, with no muscle output.
modulation
Modulation is by norepinephrine, serotonin, dopamine, and acetylcholine secretions from pons reticular-activating-system neuron axons. Awakeness has high norepinephrine, serotonin, and dopamine and low acetylcholine. REM sleep has low norepinephrine and low serotonin but moderate dopamine and high acetylcholine. NREM sleep has neither high nor low neurotransmitter levels.
Cholinergic axons go to amygdala and multisensory posterolateral cortex and fire when eyes move.
cycles
Sleep has four or five cycles. First cycle has long deep NREM sleep and short REM sleep. Last cycle has long REM sleep and short shallow NREM sleep.
Consciousness>Consciousness>States>Sleep>Sleep Cycle
1-Consciousness-States-Sleep-Sleep Cycle
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Date Modified: 2022.0224