Sleep

• Sleep debt


  The amount of sleep a person needs but is not getting
• EEGs


  • Provide a record of electrical activity
  • Show characteristic EEG patterns for different sleep stages
  • Cycles in stages from 1 (light) to 4 (heavy) sleep
  • Alpha waves are relative frequent, characteristic of awake but resting state
  • Delta waves are slow, characteristic of stages 3 and 4 (slow wave sleep)
  • REM sleep looks much like waking, no waves, lots of brain activity, eye movements
  • Cycles repeat several times a night
• NREM sleep


  Non-rapid eye movement sleep
• REM sleep


  Rapid eye movement sleep
• There must be a big selective advantage to offset the risks of sleep
• Growth and Repair


  Functions of sleep for the body
• In NREM sleep, brain inactivity may allow brain repairs
• REM sleep is paradoxical because the brain is not at rest
• Aserinsky & Kleitman (1953) study

  1. IV = stage of awakening (REM vs. NREM)

  2. DV = report of dream

  3. 20 dreams /27 REM awakenings

  4. 4 (vague) dreams / 23 NREM awakenings
• Dement (1960) study


  1. Sequence: baseline, REM deprivation, recovery, NREM deprivation, recovery

  2. Manipulate time of awakening / type of deprivation (none=baseline/REM/control=NREM)

  3. Measure % REM sleep during baseline and recovery

  4. More REM following REM deprivation suggests a need for REM
• Activation-synthesis theory


  • Activation: patterned firing of cells in pons during REM, helps brain growth and possibly reset
  • Synthesis: Cortex makes sense of the activation, because that's just what cortex does! But dreams (what cortex invents to synthesize the activation) are just a by-product
• Walker (2006) study


  1. Task: learn finger tapping sequence

  2. IV: timing of sleep (between learning and testing, or after testing)

  3. DV: speed and accuracy

  4. Subjects were faster and more accurate if they slept after learning

  5. Slow wave sleep was the key factor
• Li, Ma, Yang & Gan (2017) study

  1. IV: Rem deprivation vs. NREM deprivation

  2. DV: dendrite growth following learning, measured with an electron microscope

  3. Mice that learn a new task grow new dendrites

  4. REM sleep helps to prune some of those dendrites, allowing and encouraging others to grow
• Patients with brain stem lesions have no REM sleep, but still learn