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Individual Differences in Biofeedback Performance: EEG Alpha, Skin Resistance, and EMG

Understanding individual differences in biofeedback performance may help elucidate the mechanisms of biofeedback and aid in identifying the treatment of choice in clinical settings. Although many studies have attempted to relate biofeedback performance and personality measures (e.g., Ray, 1974). one fundamental problem has received little attention, namely, the extent to which an individual's success in biofeedback is task-specific vs consistent across physiological responses. The present study examined biofeedback performance across three biofeedback tasks. The 36 participants, 18 males and 18 females, ages 13 to 59 yr., received three biofeedback sessions, one each for electromyogram (EMG) reduction, bi-directional EEG alpha control, and bi-directional skin resistance control, with the order of the sessions counterbalanced. For EMG, a BIT Model 401 device measured frontalis EMG and provided audio feedback. After a 5-min. baseline the participants attempted to reduce EMG for 24 min. For EEG alpha, BFT Model 115 and 215c devices measured integrated EEG alpha from 01 referenced to A1 and provided audio feedback. After a 5-min. baseline, the participant attempted successively to increase and decrease EEG alpha across two 12-min. segments. The procedure was identical for skin resistance. A BFT Model 701 device monitored skin resistance from finger electrodes on the dominant hand and provided pitch-proportional audio feedback. There was significant reduction of EMG from the first one-half of training, 24.4 pV (peak-tepeak), to the second, 19.4 pV (F1.a = 46.40, p < .001). There was no significant self-regulation of skin resistance over-all, with means of 20.0 KQ during resistance increase vs 19.9 KR during resistance decrease (F < 1.00). There was self-regulation of EEG alpha with means of 5.33 pV during EEG alpha increase vs 4.83 pV during EEG alpha decrease (FI.~, = 7.25, 9 < .01). There were no significant correlations across participants between biofeedback performance measures for the three biofeedback tasks. These results complement findings (e.g., Suter, 1977) that biofeedback effects tend to be limited to the physiological response in the feedback loop and suggest that brief periods of different types of biofeedback training do not each produce phys~ological changes along a unitary cortical-somatic dimension of activation-inhibition.