FACIAL EMG RESPONSES TO AUDITORY-STIMULI

Three studies were performed to investigate the effects of auditory st imuli (pure tones and environmental noise) of different intensities on surface EMG activity recorded over five facial muscle regions (M. fro ntalis lateralis, M. corrugator supercilii, M. orbicularis oculi, M. z ygomaticus major, M. depressor anguli oris). The results show that wit h presentation of tones and noises of high intensity (> 85 dB) strong facial EMG reactions over muscles of the upper face (M. frontalis late ralis, M. corrugator supercilii, M. orbicularis oculi) were evoked. Am ong environmental noises of different valence but the same intensity, baby's crying evoked EMG reactions over facial muscles in the mouth re gion, possibly indicating that the subjects demonstrated expressions o f dislike during this particular stimulation. It is also discussed whe ther facial EMG reactions to auditory stimulation of different intensi ties could be connected to changes in muscle tone of the middle ear mu scles. The contraction of these muscles modulates sensitivity to audit ory stimulation. Thus, facial EMG activity of the muscles of the upper face could serve as an indicator of sensitivity to external auditory stimuli. However, the evaluation of pleasant and unpleasant emotional reactions in response to auditory stimulation seems to be impossible.