Lab 3: Electroencephalogram 

• Electroencephalogram (EEG) : recording of electrical activity from cortical neurons of the brain
    * Correlation between activity level or level of input and synchronization of cortical neurons
      * Neurons will depolarize as long as individual is alive, regardless of activity or input level
      * Activity or input level determines depolarization pattern
        * Increased input → decreased synchronization → increased frequency
          * Neurons respond and depolarize as sensory input arrives
        * Decreased input → increased synchronization → decreased frequency
          * Neurons synchronize and depolarize together
    * Named wave patterns defined by range of frequency and amplitude
      * Overall wave pattern named for wave type that dominates
      * Amplitude and frequency inversely related
      * Beta: 14-30 Hz, 5-10 μV, active, alert, and focused
      * Alpha: 8-13 Hz, 8-14 μV, awake but drowsey, not active/not focused, daydreaming
      * Theta: 4-7 Hz, 100 μV, light sleep
      * Delta: 0.5-3 Hz, 20-200 μV, deep sleep, unconscious

• Sleep
    * Awake
      * Transition from Beta to alpha waves (due to cutting off visual input - eyes closed)
    * Four numbered stages (or three numbered stages depending on source) of slow wave or non-REM (NREM) sleep
      * Sleep stage 1 (SWS1 or NREM1) – brief transition between awake state and sleep state, transition from alpha to theta waves
        * Slow eye movement and floating sensation
      * Sleep stage 2 (SWS2 or NREM2) – Light sleep with theta dominant wave pattern
        * Sleep spindles only occur in stage 2 as response to stimulus → stay asleep/not wake up (higher average of sleep spindle = better sleep)
        * Slight decrease in breathing and heart rate
        * Eyes generally still
      * Stage 3 and 4 (SWS3 and 4 or NREM3 and 4) - deep sleep, delta wave dominant pattern
        * Oblivious sleep
        * Decrease in body temp, breathing, and heart rates
        * Unconscious shifts in position
        * Sleepwalking
      * REM (rapid eye movement) - high frequency beta-like wave pattern
        * Called paradoxical sleep due to the high frequency pattern
        * Atonia - paralysis of voluntary muscles (sleep paralysis), only extraocular muscles and diaphragm remain active
        * Most vivid dreams
    * Cycle through stages
      * Early cycles include deep sleep
      * Later cycles only stage 2 and REM
      * Cycles “shortcut” as time progress

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