Electroencephalogram EEG: Measuring Brain Waves

1
Electroencephalogram (EEG) Measuring Brain Waves
2
Function of EEG

• The EEG uses highly conductive silver electrodes
  coated with silver-chloride and gold cup
  electrodes to obtain accurate measures use
  impedance device to measure effectiveness,
  resistance caused by dura mater, cerebrospinal
  fluid, and skull bone
• Monopolar Technique the use of one active
  recording electrode placed on area of interest, a
  reference electrode in an inactive area, and a
  ground
• Bipolar Technique the use of two active
  electrodes on areas of interest
• Measures brain waves (graphs voltage over time)
  through electrodes by using the summation of many
  action potentials sent by neurons in brain.
  Measured amplitudes are lessened with electrodes
  on surface of skin compared to electrocorticogram
  

3
Sodium-Potassium Pump

• The mechanism within neurons that creates action
  potentials through the exchange between sodium
  and potassium ions in and out of the cell
• Adenosine Triphosphate (ATP) provides energy for
  proteins to pump 300 sodium ions per second out
  of the cell while simultaneously pumping 200
  potassium ions per second into the cell
  (concentration gradient)
• Thus making the outside of the cell more
  positively charged and the neuron negatively
  charged
• This rapid ionic movement causes the release of
  action potentials

4
History

• Richard Caton (1875) localization of sensory
  functions with monkeys and rabbits
• Hans Berger (1924) first EEG recording done on
  humans- described alpha wave rhythm and its
  suppression compared to beta waves
• - acknowledged alpha blockade when subject
  opens eyes
• William Grey Walter influenced by Pavlov and
  Berger, further developed EEG to discover delta
  waves during sleep (1937) and theta waves (1953)

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Alpha Wave

• Characteristics - frequency 8-13
  Hz-amplitude 20-60 µV
• Easily produced when quietly sitting in relaxed
  position with eyes closed (few people have
  trouble producing alpha waves)
• Alpha blockade occurs with mental activity
  -exceptions found by Shaw(1996) in the case of
  mental arithmetic, archery, and golf putting

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Beta Waves

• Characteristics-frequency 14-30 Hz-amplitude
  2-20 µV
• The most common form of brain waves. Are present
  during mental thought and activity

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Theta Waves

• Characteristics-frequency 4-7Hz-amplitude
  20-100µV
• Believed to be more common in children than
  adults
• Walter Study (1952) found these waves to be
  related to displeasure, pleasure, and drowsiness
• Maulsby (1971) found theta waves with amplitudes
  of 100µV in babies feeding

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Delta Waves

• Characteristics-frequency .5-3.5
  Hz-amplitude 20-200µV
• Found during periods of deep sleep in most people
• Characterized by very irregular and slow wave
  patterns
• Also useful in detecting tumors and abnormal
  brain behaviors

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Gamma Waves

• Characteristics-frequency 36-44Hz-amplitude
  3-5µV
• Occur with sudden sensory stimuli

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Less Common Waves

• Kappa Waves-frequency 10Hz-occurred in 30 of
  subjects while thinking in Kennedy et al.(1948)
• Lambda Waves-amplitude 20-50µV-last 250 msec,
  related to response of shifting visual
  image-triangular in shape
• Mu Waves-frequency 8-13Hz-sharp peeks with
  rounded negative portions (7 of population)

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Alternative Neuroimaging Techniques

• Positron Emission Technique (PET)- picture
  image of brain giving information about glucose
  and oxygen structures in the brain, blood flow,
  and blood volume in the brain-advantage compare
  cross-sections of brain regions simultaneously
  -disadvantage findings may be caused by
  inhibitory neurons
• Functional Magnetic Resonance Imaging
  (?MRI)-picture image of anatomical structures,
  derived from magnetic imaging -allows for
  measurement of blood oxygen concentration, blood
  flow, and blood volume -advantage see ongoing
  changes as well as strong spatial resolution, and
  quick/effective data collection

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Alternative Methods (cont)

• Biomagnetism -Measures magnetic activity given
  off by the brain -Super conductive quantum
  interfering device (SQUID)-disadvantage very
  difficult to pick up these small magnetic
  measures due to environmental magnetic forces
• Magnetoencephalogram (MEG)-similar to EEG in
  that it combines the activities of millions of
  neurons -advantages no reference electrode,
  some currents can only be found magnetically,
  scans field patterns of brain allowing for
  simultaneous area activity-disadvantage data
  not as clear and device is very susceptible to
  noise

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The EEG and its Many Applications
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Research and Application

• Psychological Research
• Neurological Research
• Medical Research
• Educational Research and Application
• Therapeutic Application
• Occupational Application

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How Effective is the EEG?

• A great deal of controversy has surrounded the
  use of EEG in tests for such topics as
  Intelligence and mental performance.
• Criticism, however, is familiar to any aspect of
  research in the scientific world.
• As a result of the critiques and of technological
  advances, procedures, measurements, and results
  have become more precise, reliable, and valid.
• In order to the best and most accurate
  information from EEGs, though, researchers agree
  that further investigation and ongoing research
  is necessary.

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• The EEG has become a widely used and successful
  research tool
• It is a practical candidate that offers valid
  measurement
• It contributes objective information that can be
  easily viewed and measured
• It is a versatile system that allows for a
  diverse application of the information it
  provides

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• Hemispheric Asymmetries Hemispheric
  Lateralization/ Specialization
• Desynchronization

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Right and Left Brain Characteristics

• Right Brain
• Spatial processing
• Musical tasks
• Left Brain
• Verbal processing
• Mathematical skills
• Emotions have also been correlated with
  differential hemispheric processing (Davidson,
  Schwartz, Saron, Bennett and Goleman, 1979)
• (Andreassi, John L., Psychophysiology Human
  Behavior and Physiological Response, 2000).

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Stimulus Complexity

• An investigation was conducted by Berlyne and
  McDonnel (1965) in order to study the effects of
  the complexity of the stimulus/stimuli on the EEG
  alpha wave. Their hypothesis was confirmed as a
  result of EEG records that demonstrated that
  higher levels of complexity produced longer alpha
  desynchronization periods.
• (Andreassi, John L., Psychophysiology Human
  Behavior and Physiological Response, 2000).

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Tasks of Vigilance and Attention

• In order to study attention ability Ray and Cole
  (1985) investigated participants intake and
  rejection of stimuli.
• The results showed that alpha power was greater
  in the right hemisphere during rejection.
• Beatty, Greenberg, Deibler, and OHanlon (1974)
  found that EEG readings demonstrated that
  suppression of theta activity and rhythm helped
  to better maintain vigilance while performing
  tasks.
• (Andreassi, John L., Psychophysiology Human
  Behavior and Physiological Response, 2000).

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Hypnosis, Imagery, Meditation and Perception

• Traditionally, the lines between the four
  greatly related mind states were not very clear.
  Research conducted with the use of EEG, however,
  has enabled researchers to draw more distinct
  lines between each of the topics, and to study
  the distinct characteristics of each of them.

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Hypnosis

• EEG during hypnosis has contributed to the
  knowledge that it is not a stage of deep sleep,
  rather a modification of the waking state
• MacLeod, Morgan and Lack (1982) conducted a dream
  task study during hypnosis using EEG.
• The results demonstrated a shift from greater
  left hemisphere activity, to right in highly
  hypnotizable participants, and no such shift in
  low hypnotizable participants.
• A related study conducted by DePascalis and
  Perrone (1996) revealed that participant pain
  ratings decreased when an analgesic state was
  suggested during hypnosis
• The EEG records showed a decrease in EEG
  amplitude in the right hemisphere during the
  above mentioned condition.
• (Andreassi, John L., Psychophysiology Human
  Behavior and Physiological Response, 2000).

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Imagery

• Gale, Morris, Lucas and Richardson conducted a
  study in 1972 in which imagery was measured on a
  vividness scale, while the occipital area was
  recorded using EEG.
• The results of the EEG showed a definite decrease
  in Alpha activity during all but one of the
  imagery tasks.
• Williamson and Kaufman (1989) later integrated
  the Magnetoencephalograpy (MEG) to study
  suppression of alpha activity in the visual
  cortex during mental imagery.
• (Andreassi, John L., Psychophysiology Human
  Behavior and Physiological Response, 2000).

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Meditation

• Results from a study conducted by Elson, Hauri,
  and Cunis (1977) were collected and based on EEG
  information.
• The EEG readings from the meditating group
  demonstrated stable alpha and theta activity, and
  none fell asleep.
• The EEG records from the non-meditating group, on
  the other hand, revealed K-complexes and sleep
  spindles. A total of six of the participants
  from the group fell asleep.
• (Andreassi, John L., Psychophysiology Human
  Behavior and Physiological Response, 2000).

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Sensation, Perception and EEG

• Studies have indicated that our perception and
  sensations may have substantial effects on mood
  and emotional states.

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• EEG records showed that sound sensitivity was
  lower during periods of alpha activity than
  during non-alpha activity.
• In 1998 Martin evaluated previous information
  about the effect of odor on EEG and mood,
  conducting two of his own studies, and was able
  to report a variety of effects.
• He believed that previous investigations produced
  different results due to a difference in EEG
  recording.
• The results of his own carefully controlled
  experiments supported a correlation between odor
  and EEG activity.
• Real food odors, such as chocolate, were
  linked to extremely low theta levels and received
  the highest participant ratings for relaxing
  effects and pleasantnessrevealing the capability
  of odors to change EEG activity.
• (Andreassi, John L., Psychophysiology Human
  Behavior and Physiological Response, 2000).

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The Awesome EEG

• It is plain to see that EEG has offered a number
  of great advances in research. It has
  demonstrated its versatility and usefulness in
  the many diverse areas that it has been utilized.
  From therapeutic endeavors, and enhancing
  educational efforts, to offering information and
  insight that has helped to improve pilots,
  conductors, and drivers vigilance performance,
  as well as strengthening the base of general
  knowledge in a way that has helped to improve our
  everyday lives .

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Conditioning of The EEGSleep and The EEG
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• Conditioning of the EEG

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Classical Conditioning (EEG)

• Pairing of conditioned and unconditioned stimuli
  to warrant a conditioned response.
• EEG recordings found changes in neural activity
  with the presence of CS (Condition stimulus).
• In EEG experiments that involve conditioning
• -alpha blocking occurs with respect to the CS
  after many pairing
• of a CS and US.
• -The UR (unconditioned response) is a natural
  alpha blocking process.
• -Classical conditioning Is usually
  done with the participant being asleep.

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• CS ? US ? UR Natural alpha
  blocking , the CS alone cannot
• (light) (tone) (no response)
  sustain alpha blocking
• after several pairings
• CS ? US ? UR
• (light) (tone)
• CS ? US ? UR Trying to sustain CS
  alpha blocking W/
• (light) (tone)
  multiple pairings of US.
• CS ? US ? UR
• (light) (tone)
• finally
• US ? CR The US has now been shaped to
  create the CS.
• CS ? CR The new CS creates the same CR as
  the previous CS. The new CS can
  now generate alpha blocking on its own.

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Operant Conditioning (EEG)Can it be done?

• Done while participant is awake.
• Studies include work with people suffering from
  seizures (epileptics), and their progress.
• Studies w/ operant conditioning shows results of
  other disorders being alleviated (biofeedback).
  I.E. Migraines
• Studies are being done to see if people can
  control which brain waves they can produce (alpha
  and theta) with the onset of a signal or tone.
• Most people could not produce alpha and theta
  waves on command w/o the signal or tone being
  given
• Researches tried to alter mood with alpha waves
  as well.
• All in all, operant conditioning of EEG has been
  deemed possible

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Non-contingent stimuli (operant conditioning)

• Expectancy effects
• - Subjects who were led to believe that they
  enhanced
• alpha were actually able to control alpha
  better than
• those who believed they suppressed
  alpha.
• Biasing effects
• - Experimenters expectations were found to
  influence EEG alpha
• measures in the direction of the
  expectation.
• Controls
• - Controls are effective and necessary in
  non-contingent stimulation studies in
• operant conditioning studies. A.
  increase in alpha could be due to randomness or
  non-contingent stimuli.

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• Sleep and The EEG

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Sleep and EEG

• Sleep studies are very hard to conduct.
• - Takes many nights to conduct a full study
• - Patience is a must both participants and
  experimenters
• Benefits of sleep studies
• - Better understanding in studies
  involving
• A. Human performance
• B. Behavior
• C. Well-Being

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Sleep and EEG contd

• Sleep studies began in the 1800s
• 1930s EEG recording machines began to make an
  appearance.
• Todays sleep laboratories have many different
  kinds of physiological machines and recorders
  such as
• EEG
• EOG (electroculogram)
• EMG (electromyogram)
• Rectal temperature
• Respiration
• (Any measurements made by these machines are
  called- Polysomnograms)

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Sleep and EEG contd

• Different stages of sleep and their respective
  brain waves
• Stage 1 Low voltage random EEG activity (2-7 Hz)
• Stage 2 Irregular EEG pattern/negative-positive
  spikes (12- to 14- Hz)
• Also characterized with sleep spindle and
  K-complexes that could occur every few seconds.
• Stage 3 Alternative fast activity, low/high
  voltage waves and high amplitude
  delta waves or slow waves (2 Hz or less).
• Stage 4 Delta waves
• Stage REM (Rapid eye Movement) episodic rapid
  eye movements, low v voltage
  activity.
• Stage NREM All stage combined, but not including
  REM or stages that may contain REM.
• The K-complex occurs randomly in stage 2 and
  stage 3
• The K complex is like an awaken state of mind in
  that is associated with a response to a stimulus
  that one would experience while awake.

38
EEG and Dreaming

• REM was discovered in 1953 by Aserinsky and
  Kleitman.
• REM was observed as fast eye movements that moved
  in many directions while a person was asleep.
• REM varied in amplitude and lasted 1 second or
  less.
• Studies showed that people remember dreams 75
  (60-90) more when waken during REM sleep, If
  not woken during REM sleep dreams are only
  remembered 7 of the time.
• NREM dreams are described as being less active
  and less vivid
• Therefore, there are both qualitative and
  quantitative differences when discussing REM and
  NREM sleep.

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Dream Studies

• The first dream studies were interested in
• Changing dream content
• Drugs and their effects on dreaming
• Pre-sleep stimulation and dreaming
• Dream content with respect to patients that had
  different psychiatric disorders

40
REM Dreaming

• Most early research was concerned with lucidity
  of REM Dreaming.
• Meaning one could shape what they dreamed in
  choosing what they would dream about.
• Come to the realization that one is dreaming
• High amplitude EEG alpha waves.
• Higher in the beginning of REM, and lower in end
  of REM.
• Higher amplitude waves are also characterized of
  bizarre, and emotional dreams.
• Ongoing lucid studies are being conducted to see
  if lucid content come from prelucid dreaming.
• Questions the relationship between REM alpha
  waves and Lucidity

41
Deep sleep and Responsiveness

• Light sleep (stages 12)
• Deep sleep (stages 34)
• Sleep is cyclical
• Meaning that one will usually go from light sleep
  to deep sleep back to light sleep again.
• The whole cycle take about 1 and ½ hours (90
  min.)
• Stage 3 and 4 are hard to obtain, due to light
  sleep occurring more towards the end of a sleep
  cycle.

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EEG brain waves in the Sleep Cycle
43
Sounds and sleep

• Studies found it was more difficult to wake up a
  person during latter stages of sleep, even with
  very loud sounds.
• Fire alarm study
• Researchers looked at how long it would take for
  someone in a certain stage of sleep to turn off
  the aversive stimulus (Alarm).
• They found People in stage 1 sleep were more
  likely to turn off the aversive stimulus quicker
  than all other stages.
• Researchers also found that meaningful stimuli
  awakened people quicker than non-meaningful
  stimuli.

44
Work and Exercise and how it effects sleep EEG
(Kripke, Cook, and Lewis 1976)

• Work (hospital employees)
• - Hospital employees experience a reversal in
  the sleep-wakefulness
• cycle (biological effects).
• - Duration of each stage of sleep was usually
  shorter.
• - Stage 1 sleep in hospital employees was
  generally longer than typical
• stage 1 sleep in normal sleepers.
• Work (night shift- permanent)
• - Have better body temperature regulation, and
  more stable sleep
• patterns.

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Work schedule and sleep contd

• Hospital workers actually fall asleep if put on
  a rotating schedule
• (10pm 6am)
• Sleep during daytime hours takes longer, than
  nighttime hours.
• Daytime sleepers (permanent night shift workers)
  have reduced REM sleep.

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Exercise and Sleep EEG Horne and porter (1975)

• There are differences between afternoon and
  morning exercise.
• Exercise conditions do not help one to fall
  asleep easier.
• Relaxation techniques help people to fall asleep
  easier (Brownman and Tepas, 1976).
• Afternoon exercises produce increased slow-wave
  sleep/stages 3 and 4.
• (85 minutes bike ride)
• Same amount of exercise in morning had no
  effects.
• Stages 3 and 4 are known and restore and repair
  stages.
• However, people that exercise do not experience
  longer durations of sleep in stages 3 and 4 or
  SWS (Brownman and Tepas, 1976).
• Bunnel, Bevier, and Horvath found that exercising
  to the point of exhaustion increased slow-wave
  sleep, but decreased REM.
• Therefore daytime activity can increase stage 3
  and 4 sleep/SWS as long as it is intense in
  duration.

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Sleep Deprivation

• Three different kinds (Naitoh, 1975)
• Total sleep deprivation
• missing one or more sleep periods
• Partial sleep Deprivation
• missing a section of the sleep cycle
• Differential Sleep Deprivation
• Wakening a person during different random points
  in a sleep cycle based on EEG signs of particular
  stage

48
Total Sleep Deprivation (Woodward and Nelson,
1974)

• Studied army men who experienced 2 sleep cycles
  lost
• Effects
• Memory impairment (short term memory)
• Increased irritableness
• Attention deficits (micro lapses)
• Lack of motivation
• EEG showed an increase in slow wave sleep in
  recovery

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Partial Sleep Deprivation (Webb Agnew, 1974)

• Done over a 60 day periods consisting of 5 ½
  hours of sleep each night.
• Experienced an increase in Stage 2 and 4 sleep.
• REM decreased by 25
• Vigilance decreased as experiment progressed.
• Conclusion for partial sleep deprivation
• 6 hours is needed to be vigilant
• Major behavioral differences will occur (see
  above)

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Differential Sleep Deprivation (Moses, Johnson,
Naitoh and Lubin, 1975)

• One study looked at deprivation of REM/Stage 4
  sleep deprivation and total REM sleep
  deprivation.
• REM/Stage 4 study -2 nights vs. Total REM sleep
  -3 nights
• Needed more arousals than second experiment to
  keep them from entering stage 4 sleep.
• Concluded that Stage 4 has more importance than
  REM sleep due to sleep loss.

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Sleep onset, difficulties with EEG wave location,
experimental difficulties

• Alpha waves vary person to person, makes it hard
  to locate in stage 1 sleep
• K-complexes and sleep spindles are giveaways of a
  person being asleep
• People dont respond to certain tones during
  certain stages of sleep.
• People might not hear the tone (hearing
  impaired)- Hearing tests should be down to rule
  out this confounding variable.
• People that have insomnia (elderly men and
  women)/misperception etc.
• Insomnia causes SWS abnormalities
• Researchers would like a behavioral measure as an
  additional indicator of a person being asleep,
  but none exists.
• An ideal machine would measure finger muscle
  depression

52
Sleep onset, difficulties with EEG wave location,
experimental difficulties contd

• EEG and thermoregulartory system patterns
• Shows that drop in rectal temperature, signifies
  SWS is sustained.
• More studies must be done to confirm this.

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Summary of EEG

• Conditioning exercises prove that Alpha wave
  control may be possible.
• Discovery of REM made it possible for further
  investigations into sleep studies and various
  parts of sleep.
• The strength of a stimulus has an impact on the
  outcome of a study.
• Learning may occur during stage 1 2 of sleep
  when material is meaningful
• Dreams vary in content and emotions
• Daytime sleep differs from nighttime sleep on a
  number of levels
• Confounding variables are important in
  eliminating before conduction an EEG study.
• Selective deprivation vs. Insomnia
• Biological effects on sleep

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References

• Andreassi, J. L. (2000). Psychophysiology Human
  Behavior Physiological Response (4th ed.)
  Mahwah, New Jersey Lawrence Erlbaum Associates,
  publishers.
• Sleep Holsitconline.com. (1998-1999). The
  different stages of sleep Chart. World Wide
  Web. Retrieved September 10th, 2006, from
  http//holisticonline.com/Remedies/Sleep/sleep_st
  ages-1- 4NREM.htm
• (1996, October 11). The Electro-Physiology Of
  Sleep. Retrieved September 9th, 2006, from
  http//ourworld.compuserve.com/homepages/dreamthe
  mes/a ge31.html

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References contd

• Cell Biology. (2005, January 11). Cell Biology.
  Retrieved September 9th, 2006, from
  http//www.nurseminerva.co.uk/cell.html
• Wikipedia. (2006, September 9).
  Electroencephalography Chart. World Wide Web.
  Retrieved September 8th, 2006, from
  http//en.wikipedia.org/wiki/Electroencephalogram
  
• Wikipedia. (2006, September 10). Hans Berger.
  World Wide Web. Retrieved September 9, 2006,
  from http//en.wikipedia.org/wiki/Hans_berger