Ultradian Rhythms

• Ultradian rhythms occur multiple times in a 24 hour period.
• A sleep pattern occurs in 90 minute periods divided into 4 stages. Each characterised by a different level of brainwave activity.
• Stage I -

  Light sleep that occurs between being awake and asleep. At the beginning alpha waves are present and then change to theta waves before the end of the stage. It’s common to experience hypnogogic hallucinations such as hearing someone call your name or seeing words if you were reading. You can also experience the feeling of falling or hypnic jerks such as twitches.
• Stage 2-

  Slightly deeper sleep accompanied by theta waves where its still fairly easy to wake a person. K-complex and sleep spindles are experienced. During a k-complex when someone touches your arm in your sleep, the brain processes this and if safe the it will suppress cortisol arousal so you don't wake up. Sleep spindles inhibit certain cognitive perceptions.
• Stage 3 -

  Slow wave sleep accompanied by delta waves where the person is dead to the world and incredibly hard to wake up. In this stage memory is transferred to LTM and its most possible to sleepwalk or sleeptalk at this point.
• Stage 4 -

  REM sleep is also known as paradoxical sleep since the body is paralysed but the mind is active. Beta waves are present which is similar to how we are when were awake. Its the state in which we dream but can also experience sleep-paralysis. Eyes move under eyelids.
• Stage 1 -> 2 -> 3 -> 2 -> 4