Hypnic Jerk

Hypnic jerk

  • Involuntary twitch
  • Rapid heartbeat, quickened breathing, sweat
  • Anxiety, caffeine, stress and strenuous activities in the evening, can be random
  • Evolution (primate ancestors) – could be a reflex to the brain’s misinterpretation of muscle relaxation with the onset of sleep as a signal that a sleeping primate is falling out of a tree
  • Occurs during non-rapid eye movement stage of sleep (not usually where dreams occur)
  • Illusion of falling

Great optical illusion!  See more: http://www.interestingenginering.com: