Figure 4. Effects of mental stress on hemodynamics of the masseter muscle. OxyHb, oxygenated hemoglobin; DeoxyHb, deoxygenated hemoglobin; TotalHb, total haemoglobin (OxyHb + DeoxyHb); StO₂, tissue blood oxygen saturation (OxyHb/TotalHb x 100); 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 < 0.1, ** p < 0.01, *** p < 0.001 (Scheffé).