EMG activities of facial and chewing muscles of human adults in response to taste stimuli

To evaluate facial expression patterns induced by different taste stimuli, electromyograms (EMG) of the facial and chewing muscles of 12 healthy university students, aged 20 to 23 years, were analyzed. Sucrose (sweet), NaCl (salty), citric acid (sour), quinine-HCl (bitter), monosodium glutamate (MSG; umami), homogentisic acid (harsh), tannic acid (astringent), and capsaicine (pungent) were the taste stimuli used. Rating scale tests were made to assess the hedonics (pleasantness) of the taste stimuli. EMG responses of the corrugator supercilii, venter frontalis, orbicularis oculi, depressor anguli, and digastricus muscles to capsaicine, tannic, acid, and citric acid showed larger amplitudes than to NaCl, MSG, homogentisic acid, and sucrose. Increases in EMG responses for most facial and chewing muscles for the taste solutions had significant negative correlations to the solutions' hedonic scale values. Most facial and chewing muscles of adult humans therefore showed greater responses to disliked than to preferred or less preferred tastes.