CHAPTER 3

I. EEG Rhythms

EEG first recorded by Caton in 1875 from the cortex of rabbits and monkeys, later recorded from surface electrodes in humans by Berger in the 1920's.

A.Source of the EEG

Exact nature of EEG is unknown, whether it represents spatially and temporally summed action potentials and/or IPSPs and EPSPs, but is clearly the results of the synchronous activity of large populations of neurons.

B.Traditional EEG frequency bands

Historically identified visually from polygraph recordings as a "dominant" rhythm.

 

 

1.Alpha - frequency = 8 -13 Hz, amplitude = 20-60 V, dominant frequency during "relaxed wakefulness"
2.Beta - frequency = 14-30 Hz, amplitude = 2-20 V, dominant frequency during mental and physical activity
3.Delta ) - frequency = 0.5 -3.5 Hz, amplitude = 20-200 V, dominant frequency during deep sleep
4.Theta (Y) - frequency = 4 -7 Hz, amplitude = 20-100 V, dominant frequency for children, in adults increases with drowsiness and attention (at frontal sites)

C.Special EEG rhythms

1.Kappa - frequency = 10 Hz, only occurs in about 30% of subjects during thinking (rarely used)
2.Lambda - amplitude = 20-50 V in occipital areas after visual stimulation
3.Mu - frequency = 9-11 Hz in superior temporal cortex, occurs in about 7-8% of the population

D.Sleep Rhythms - EEG rhythms observed only during sleep.

1.sleep spindles

2.K-complexes
3.rapid eye movements (REM)

II. EEG Recording

A. Electrode sites (montage) - The International 10-20 System (Jasper, 1958)

B. Reference

1. Monpolar - active site refrerenced to inactive site such as earlobe or mastoid.
2.Bipolar - two active sites referenced to each other, results in the arithmetic difference between sites (used in sleep and clinical EEG, but not much in other research).

III. EEG and Motor Performance

A. Reaction Time

1. Adults - no consistent relation between EEG and RT
2.Children - Surwillo (1971) is typical, higher frequency EEG associated with faster RT, but RT decreases with age and EEG frequency increases with age. EEG accounts for a very small percentage of the RT-Age variance.

B.Visuomotor

1.Sterman et al. (1983) study - greater right parietal alpha suppression to fueling task than to 10 degree turn. Greater bilateral temporal alpha supression to visual than to instrument landing.
2.Backs et al. (in prep) study - parietal alpha suppression and frontal theta enhancement for dual task conditions than for single task conditions.

IV. EEG Asymmetries

Need to use only strongly RH subjects.

A. Gevins et al. (1980) criteria for EEG asymmetry

B. Asymmetries that meet most Gevins et al. criteria

1. Davidson & Schwartz (1977)
2. Rugg & Dickens (1982)
3. Davidson et al. (1990)

VI. EEG and Emotion

Greater EEG activity in left frontal lobe for positive emotions and greater EEG activity in right frontal lobe for negative emotions for both infants and adults.

VII. EEG and IQ

No consistent relationship between EEG and IQ for children or adults.