Biofeedback training of 40Hz EEG activity in humans : relationships to cognitive performance, voluntary control, subjective states and autonomic activity

Forty Hertz EEG was examined in a group of 49 male university students during problem-solving tasks and during resting baseline conditions. Following the completion of the Pre-Test problem-solving phase subjects were then trained, using biofeedback procedures, to either increase or suppress UOHz EEG and were again tested on the Post-Test which was an equivalent form of the Pre-Test. Thirty-two subjects completed this phase of the study. Forty Hertz EEG and beta (21-30Hz) were recorded from the O2-P3 lead in 25 subjects during the Pre-Test condition. Forty Hertz EEG was recorded from the Cz-01 and Cz-02 leads, and theta, alpha and beta were recorded from either Cz-O^1 or leads in 24 subjects. Forty Hertz muscle activity was monitored from the left or the left and right neck-temporal muscle for all subjects. Forty Hertz and 70Hz from the muscle leads were compared using coincidence detectors to prevent counting UOHz generated from the muscle leads as EEG responses. EEG and muscle filters were set to trigger a digital output when three cycles of electrical activity was present. Heart rate was recorded from a total of 1U subjects. Thirteen subjects were given a Control Test following biofeedback training to measure the degree of voluntary control in the absence of feedback. Subjective state analysis was performed on a total of 31 subjects at various stages in the experimental sequence. Q-Sort items, representing descriptions of theta, alpha, beta and 40Hz EEG states were sorted into four subjective feeling categories. The following results were obtained: 1. Forty Hertz EEG was significantly greater during problem solving as compared to a resting baseline. 2. Following biofeedback training, subjects who were conditioned to increase hOHz EEG had significantly more of this activity during the tasks condition of the Post-Test as compared to the tasks condition of the Pre-Test. Those subjects who could not be conditioned to increase 40Hz EEG had significantly less of this activity during the tasks condition of the Post-Test as compared to the tasks condition of the Pre-Test. 3. Strong and consistent dissociations between 40Hz EEG and 4OHz muscle activity, and 4OHz EEG and beta (21-30Hz) were demonstrated. 4. Significant increases in cognitive performance occurred across all groups between Pre- and Post-Tests and was probably due to a general practice effect. However, one group, trained to increase 40Hz from the O1-P3 lead, showed increases in performance that could not be completely attributed to practice effect alone. 5. Voluntary control of 40Hz EEG in the absence of feedback information was shown for nine subjects, and this control persisted at least nine weeks after training. 6. Subjective state analysis indicated high arousal and mental concentration during 40Hz increase state, and low arousal and little mental effort during the UOHz suppress state