The EEG and Behavior: Motor and Mental Activities
Many long-time EEG researchers still experience a degree of fascination and awe as they watch the pens of their physiological recorders trace out the patterns of electrical activity occurring at that instant of time in the human brain. It is very difficult to convey to an audience or a reader the sense of wonderment as the pens vibrate and quiver to the changing frequencies and amplitudes of the various brain waves. From the very beginning, the fascinating nature of EEG activity, and the fact that it was brain-generated, encouraged scientists to study relationships between brain waves and behavior. Some kinds of relationships, which seemed very logical at first, have proved very elusive to establish. One example is the effort expended in attempts to relate intelligence to EEG activity. No doubt this has been due, at least in part, to the tremendous complexity of the brain itself, and to difficulties in the interpretation of large masses of EEG data. Nevertheless, researchers have pursued questions of brain wave--behavior relationships, and a great deal of effort has been expended on this topic.
This chapter explores the effect that cognitive and physical activities have on EEG wave- forms. Variations in EEG that occur with the movements involved in reaction time and other motor activities are discussed first, and then the question of whether EEG patterns can serve as an objective indicator of intelligence is considered. Right and left hemispheric asymmetries, or differences in EEG pattern as a function of type of task, remains a topic of interest to psychophysiologists. One issue among the asymmetry studies concerns the nature of differential EEG in the two hemispheres as subjects experience various emotional states. Other topics include EEG during states of hypnosis, imagery, and meditation. A consideration of environmental factors affecting EEG activity is presented in chapter 19.
This section first examines the relationship between EEG recordings and simple motor reaction time. Then, under the subheading of visuomotor performance, we consider EEGs measured simultaneously with more complex motor performance, the kind that requires continuous eye and hand coordination.
In their classic book titled Experimental Psychology, Woodworth and Schlosberg ( 1954) noted that reaction time (RT) includes the time it takes for a sense organ to react to some stimulus, brain processing time (to carry impulses to and from the brain), and muscle time (the