The Complexity of Electroencephalographic Signal Decreases during the Social Stress

Social stress affects brain function. Trier social stress test (TSST) is a standard test to assess it. The study aimed to analyze the electroencephalographic (EEG) recording during and after TSST in healthy subjects. The EEG signals of 44 healthy men participating in the study were recorded in the control condition, during and after TSST and after 30 min of recovery. Salivary cortisol (SC) and the Emotional Visual Analog Scale (EVAS) score were measured in the control condition, after TSST, and after the recovery period. The false discovery rate correction was used to control the false positive of significance in EEG. In the comparison control condition, the SC and EVAS levels significantly increased after TSST. The relative Delta band frequency significantly increased during TSST. On the other hand, the Beta bands and, in less amount, the Theta and Gamma 1 (30–40 Hz) oscillations decreased, especially in the frontal region. The nonlinear features such as, approximate and spectral entropy, Katz fractal dimension behaved like Beta band oscillation. All changes returned to baseline after TSST except the increase of Katz in the F3 channel after the recovery period. Thus, stress on EEG increased low frequency (1–4 Hz), decreased high frequency (13–40 Hz), and complexity indices during TSST.