| Sleep stage | EEG | Notes |
|---|---|---|
| Non-REM stage 1 (N1) | Theta waves | Light sleep |
| Transition to this stage be associated with hypnic jerks | ||
| Non-REM stage 2 (N2) | Sleep spindles + K-complexes | Deeper sleep |
| Represents around 50% of total sleep | ||
| Non-REM stage 3 (N3) | Delta waves | Deep sleep |
| Parasomnias such as night terrors, nocturnal enuresis, sleepwalking | ||
| REM | Beta-waves | Dreaming occurs |
| Loss of muscle tone, erections |
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N1 → N2 → N3 → REM Theta → Sleep spindles/K-complexes → Delta → Beta The Sleep Doctor's Brain
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Awake (eyes open) = Beta (highest frequency, lowest amplitude)
Awake (eyes closed) = Alpha
During the REM stage of sleep there is normally atonia to prevent individuals acting out their dreams. REM sleep behaviour disorders (REM parasomnias) are characterised by loss of this normal atonia during REM sleep. REM sleep is the deepest stage of sleep where dreaming occurs. It is believed that loss of muscle tone during this stage of sleep is partly a protective factor to prevent harm to oneself and others. In REM sleep disorders, the paralysis that normally occurs during REM sleep is incomplete or absent, allowing the person to 'act out' his or her dreams, which are often vivid, intense, and violent.
Sleep paralysis
Sleep disorder – either during falling asleep or waking up
Temporarily experiences inability to move, speak and react
Transitional state bet wakefulness and sleep
Characterized by inability to move muscles+terrifying hallucinations(person/supernatural creatures or terrifying individual + feeling pressure on chest and difficult breathing, feeing of dread or feeling abducted by aliens
Pathophysiology – disrupted REM sleep that induce complete muscle atonia to prevent sleepers from acting out their dreams. Normally, muscle tone regained before wake up
But the sequence is reversed resulting in the person regain conscious while muscles are still in atonic state
Proposed Risk factors – sleep disruption, traumatic life events, anxiety, depression, use of antidepressant (SSRI and lesser with SNRI)