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Electroencephalogram (EEG): Measuring Brain Waves

Electroencephalogram (EEG): Measuring Brain Waves

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Electroencephalogram (EEG): Measuring Brain Waves

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  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)

  5. 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

  6. 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

  7. 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

  8. 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

  9. Gamma Waves • Characteristics:-frequency: 36-44Hz-amplitude: 3-5µV • Occur with sudden sensory stimuli

  10. 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)

  11. 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 (ғMRI):-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

  12. 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

  13. The EEG and its Many Applications

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

  15. 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.

  16. 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

  17. Hemispheric Asymmetries & Hemispheric Lateralization/ Specialization • Desynchronization

  18. “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).

  19. 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).

  20. 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 O’Hanlon (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).

  21. 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.

  22. 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).

  23. 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).

  24. 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).

  25. Sensation, Perception and EEG • Studies have indicated that our perception and sensations may have substantial effects on mood and emotional states.

  26. 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 pleasantness…revealing the capability of odors to change EEG activity. (Andreassi, John L., Psychophysiology: Human Behavior and Physiological Response, 2000).

  27. 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 .

  28. Conditioning of The EEG&Sleep and The EEG

  29. Conditioning of the EEG

  30. 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.

  31. 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.

  32. 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

  33. 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.

  34. Sleep and The EEG

  35. 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

  36. Sleep and EEG cont’d: • Sleep studies began in the 1800’s • 1930’s EEG recording machines began to make an appearance. • Today’s 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)

  37. Sleep and EEG cont’d: • 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.

  39. 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 1&2) • Deep sleep (stages 3&4) • 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.

  42. 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.

  45. Work schedule and sleep cont’d: • 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.

  46. 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.

  47. 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

  49. 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)

  50. 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.