[The course of mimetic reactions during presentation of pictures with positive, neutral and negative value].
The EMG reactions of m. corrugator supercilii, m. frontalis lateralis, m. zygomaticus major and m. depressor anguli oris in 21 male subjects were recorded during a 5-second presentation of pictures with positive, negative, and neutral valence. Compared with the m. zygomaticus activity during the presentation of pictures with neutral and negative valence, the activity in the m. zygomaticus area was prolonged during the presentation of pictures with positive valence. The response curve of m. zygomaticus activity during presentation of pictures with positive valence showed a slight negative quadratic trend with maximum activity at 3 seconds after stimulus presentation. Compared with the activity during the presentation of pictures with positive and neutral valence, the activity in the m. corrugator area was prolonged during the presentation of pictures with negative valence. The response curve of m. corrugator activity during presentation of pictures with negative valence showed a tendency toward a negative quadratic trend with maximum activity at 3 seconds after stimulus presentation. During the presentation of all pictures the activity in the m. frontalis area yielded a strong negative linear trend with maximum activity in the first second after stimulus presentation. This might be attributed to the phenomenon of "habituation." Interestingly, after the presentation of pictures with negative valence, the response curve of m. frontalis activity showed a diminished linear trend compared with the linear trends after presentation of pictures with positive and neutral valence. This might be attributed to the phenomenon of "defensive reaction."