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