Psychological Responses to Sound Stimuli Evaluated by Alpha Wave Fluctuations

Evaluation of psychological stress or state of mind remains an important problem. The anterior asymmetry and emotion model (AAE model) is a conventional and widely used method to sort baseline affective styles (approach or withdrawal) based on asymmetry of the activity in prefrontal cortices. Another method is to use alpha wave fluctuations at the frontal poles, as proposed by Yoshida. This method estimates state of mind as one point on a comfort level surface with pleasant-unpleasant and excited-calm axes that are normal to each other. The aim of this paper is to investigate the validity of the Yoshida method through the psychological responses to sound stimuli. Twenty-two healthy graduate students listened to two kinds of sound clips (scary and soothing) to induce negative and positive emotional states. The results showed that there are significant differences between the responses to scary and soothing sound stimuli in both unpleasant and excited mood states. Compared with baseline, increases in unpleasant and excited mood states were found in response to scary stimuli. However, no significant changes from the baseline state were observed in response to the soothing sound stimulus. These results suggest that the fluctuation of alpha waves recorded at both frontal poles is a valid index for the evaluation of psychological state of mind, especially for negative stimulation. Future study plans include investigating a possible relationship between the AAE model and the Yoshida method.