The control of EEG alpha rythms through intentional auditory feedback signal

Abstract

In many previous researches of pseudofeedback control, it was showed that self-persuation could promote the effects of biofeedback. In most of these studies, the effects of HR biofeedback or EMG biofeedback were reported. Our experimental study was designed to examine the effect of intentional feedback signal on alpha feedback training. After the base-line period, during which 10 sessions were used to assess the effect of alpha enhancement in relaxation and biofeedback training, 8 subjects were devided into 2 groups, that is, Group A (correct feedback) and Group B (intentional feedback). The threshold of the feedback signal in Group A was the same value as that during the pre-training period (20μV). But the threshold of the feedback signal in Group B was varied according to the experimenter's intention (25μV or 15μV). At first, Group B subjects were not told that fact, so they had believed that the auditory biofeedback signals were the same sorts as before. Then Group A and Group B received 20 sessions of training. The results of this experiments showed as follows : When the threshold was set upward, the quantifications of the feedback signals were decreased and alpha activities of the subjects were suppressed, and when the threshold was set downward-the quantifications of the feedback signals were increased-alpha activities were enhanced. Subsequently, we examined the effect of intentional feedback signal when Group B subjects were told the experimenter's intention. In this case, in spite of the threshold was set upward, alpha activities were enhanced more and more. And when threshold was set downward, alpha activities were not so much enhanced. It is considered that the feedback signals to the nervous control center include not only the signals transmitted from the biofeedback instruments but also the subject's psychologically estimated values. The psychological estimation of the subject depend upon his self-suggestion. Therefore, by the results of our experiments, it was concluded that self-persuation played an important role in alpha activity increasing.