(A–C) Time-frequency representations of the power response relative to pre-stimulus baseline (−2000 to −200 ms) for neutral (A), positive (B), and negative (C) valence stimuli, respectively. Significant clusters (p<0.05, non-parametric permutation test) are encircled with a solid black line. (D) Time-frequency representation of the power response difference between negative and positive valence stimuli, showing significant increased activity of the theta/alpha band (5–10 Hz) at short latency (100–500 ms) and another increased theta activity (4–7 Hz) at long latencies (2700–3300 ms) with negative stimuli (p<0.05, non-parametric permutation test). (E, F) Normalized power of the activities at theta/alpha (5–10 Hz) and theta (4–7 Hz) band over time. Significant difference between the negative and positive valence stimuli is marked by a shadowed bar (p<0.05, t-test corrected for multiple comparison). (G, H) The average spectral power relative to baseline activity in the identified time period and frequency band for different emotional valence conditions (5–10 Hz, 100–500 ms; 4–7 Hz, 2700–3300 ms). Significant difference was observed in theta/alpha power at 100–500 ms between neutral and positive condition (t-value = 2.4312, p=0.0274, 95% CI of the difference: [1.3203 18.6235]), between negative and positive condition (t-value = 4.5010, p=0.002, 95% CI of the difference: [8.0741 22.6561]), in theta power at 2700–3300 ms between negative and positive condition (t-value = 3.6944, p=0.0045, 95% CI of the difference: [8.8765 32.3104]).