Biofeedback training of 40Hz EEG in humans: follow-up on control, generalization of effect, and maintenance of control during problem solving



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Long-term voluntary control of 40Hz EEG activity was investigated in six subjects, originally trained to increase and suppress 40Hz EEG in a previous study. The elapsed time between initial biofeedback training and follow-up control testing varied from one to three years. No practice sessions were held during this period. Subjects were first instructed to alternately produce and suppress 40Hz EEG with feedback. Feedback was terminated for subsequent periods if and when consistent control was shown. During the final session, subjects were given a battery of test items and were instructed to alternately produce and suppress 40Hz EEG while solving problems. Forty Hertz EEG was monitered from the O[lowered 1]-C[llowered z]. O[lowered 2]-C[lowered z]. P[lowered 3]-C[lowered z], P[lowered 4]-C[lowered z] leads during training and problem solving periods. Forty Hertz EMG was recorded from neck-temporal muscles. On-line comparator circuits prevented counting 40Hz EMG as 40Hz EEG. Significant control of 40Hz EEG, without feedback, was shown for five of the six subjects. One subject was erratic only in the production of 40Hz EEG. Significant control was shown to generalize to the O[lowered 1]-C[lowered z], O[lowered 2]-C[lowered z], and P[lowered 3]-C[lowered z] leads, regardless of which lead had been reinforced. The amount of 40Hz EEG during the suppression periods, while solving problems, was significantly greater than during the suppression periods without feedback. It was concluded that, following biofeedback training, long-term voluntary control of 40Hz EEG can be maintained for long periods—of time. Furthermore, though the greatest control was demonstrated at the conditioned lead, the effects did generalize to other nonconditioned leads, indicating that it is an overall state that is learned. Finally, 40Hz EEG could not be suppressed during problem solving periods as compared to suppression periods without feedback. This further supports the association between 40Hz EEG and mental activity. Other topics which were investigated were the changes in alpha and beta production during the training and problem solving sessions and the performance aspect during the 40Hz EEG production and suppression periods while problem solving. Relevance of the results of this study to the training of MBD children was discussed.