Abstract: Objective To explore the application of event-related potentials （ERP） by positive, negative, and neutral face expression images in the evaluation of mood disorders in brain traumatic patients. Methods ERP was tested by face expression images in 24 patients mainly with anxiety and depression symptoms （depression group） and 19 patients mainly with hostile and suspicion symptoms （hostile group）, respectively. The findings were compared with those of the control group. Results There were no significant differences, between the depression group and the hostile group, on latencies and amplitudes of late positive potential （LPP） induced by the three types of face expression images, except the amplitude induced by negative face expression image. Compared with the control group, the latencies were extended and the amplitudes were lower in both depression and hostile groups. Within each group, the difference of latencies induced by the three images was not significant. The amplitudes induced by negative face expression image was higher than those induced by positive and neutral face expression images, with significant differences in the hostile group and the control group （P<0.05） but not in the depression group. Conclusion Changes in latencies and amplitudes of LPP could be an objective indicator in the evaluation of mood disorders of brain traumatic patients. The LPP induced by negative face expression images could be more meaningful for patients mainly with anxiety and depression symptoms.

Key words: forensic psychiatry, mood disorders, event-related potentials, late positive potential