Sleep Disorders

Wakefulness

• Characterized by alpha frequency activities, sporadic eye movements, and a posteriorly dominant alpha rhythm that attenuates with eye-opening.

NREM sleep

• Stage N1 (5%): Attenuation of the alpha rhythm, the emergence of theta activity, and slow rolling eye movements.
  • Frontocentral beta activity can increase.

• • Young adults spend the least amount of time in NREM stage 1 sleep.
• Stage N2 (45-55%):
  • The stage at which adults spend the most time during normal sleep.
  • Characterized by the presence of either sleep spindles and/or K-complexes with theta range background activity.

• Stage N3 (15-20%):
  • a.k.a “deep sleep” or “slow-wave sleep” (no longer called “stage 4 sleep”)
  • EEG will show slow-waves and high amplitude delta waves.
  • Parasomnias tend to occur during this stage.

REM sleep

• 20-25% of sleep.
• Normally occurs ~90 minutes into sleep.
• Characterized by a desynchronized low voltage, high-frequency background.
• There will be decreased EMG activity (REM atonia).
• Sharply peaked irregular eye movements with lateral rectus spikes (see below) can be seen ON eeg. Note the lack of muscle artifact.