The following EEG phases have been recognised in sleep (a state of increased threshold of response to external stimuli):
Non-rapid eye movement, which involves the following stages: V
Stage 1: low amplitude activity, associated with slow rolling eye move- jf d ments; p
Stage 2: sleep spindles (12 Hz); high-voltage discharges or K complexes; n
Stage 3: high-voltage and very slow delta waves (1-4 Hz); occasional sleep l spindles.
Rapid eye movement sleep, which is characterised by: Low-voltage mixed-frequency desynchronised EEG pattern, as in the arousal pattern in awake subjects (paradoxical sleep); 3-5 Hz saw tooth waves; Hippocampal sinusoidal waves at 5-10 Hz; Phasic bursts of rapid conjugate eye movements; Reduced or absent skeletal muscle tone; The occurrence of dreams;
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