Figure 3. Effects of mental stress on IEMGs of the masseter and temporalis muscles. IEMG, integrated electromyographic activity; MST, mental stress task. Ordinates: values normalized to the maximum of measurements from the 6 analyzed periods (Rest1, Rest2, and MST1-4). Data are expressed as means ± SEM (standard error of the mean) (n = 12) * p < 0.001 (Scheffé).