Stages of Sleep

Overview

• Sleep is divided into stages:
  • Non-REM (Rapid Eye Movement)
  • REM

Non-REM Sleep

• Comprises the first four stages of sleep.
• Duration: First cycle takes about 60 to 90 minutes.
• Stages 3 and 4:
  • Known as slow-wave sleep.
  • Characterized by low-frequency brain waves on EEG.
  • Sleepwalking (somnambulance) occurs.
  • Consolidation of declarative memories (from short-term to long-term) occurs.

REM Sleep

• Occurs after the individual reverses back through Non-REM stages.
• First REM Stage: Lasts about 10 minutes.
• Subsequent REM Stages:
  • Increase in duration, possibly up to one hour.
• Characteristics:
  • Skeletal muscle paralysis (except for eye movement and diaphragm).
  • Brain is very active (paradoxical sleep).
  • Rapid eye movement, increased autonomic activity, and dreaming.
  • Consolidation of procedural memories.
• Sleep alternates between REM and Non-REM throughout the night:
  • Longer REM stages and less deep Non-REM sleep later in the night.

Sleep Study (Polysomnography)

• Used to diagnose sleep disorders.
• Monitors:
  • Brain waves
  • Blood oxygen levels
  • Breathing and heart rate
  • Eye and leg movements
• Disorders Diagnosed:
  • Narcolepsy: Sudden sleepiness during the day.
  • Sleep Apnea: Breathing stops and starts.
  • REM Sleep Behavior Disorder: Acting out dreams.
  • Unusual sleep behaviors: Sleepwalking, excessive movements, rhythmic movements.
  • Periodic Limb Movement Disorder: Unconscious leg movements.
  • Restless Leg Syndrome.
  • Chronic insomnia: Difficulty staying or falling asleep.

Interactive Component

• The lecture included a pause for six questions to test understanding.