The Race Effect on the Emotion-Induced Gamma Oscillation in The EEG

Emotion and race are two major aspects of human mental life that are widely regarded as distinct. However, it is still under debate whether the race affects emotion processing or not. The studies based on Event-related potentials indicated many interesting results, but conflicting conclusions to some degree. This paper presents a study on how race influences emotion cognition during a cognitive task through a time-frequency analysis of event-related electroencephalograph. In our study, a recognition task with racial facial stimuli was utilized to address the influence of race-effect and emotion on working memory. Three expressions of each face (happy-positive, sad-negative and neutral) from different races were chosen for the experiments. Since depression is characterized as a typical mental disease with emotion processing deficits, fifteen patients with depression and eighteen normal controls were chosen to participate in the experiment. The repeated measure analysis of variance (ANOVA) of Gamma EEG revealed that a significant interaction between race and emotion in the time-window 200-300 ms at the low gamma band (30-60 Hz). Subsequent analysis showed that, with other race stimuli, the average iGBA of low gamma band revealed different emotion effects, i.e. positive> negative > neutral. In addition, two trend effects were found, the emotion effect (positive>neutral>negative) for depression patients in the window of 500 ms - 600 ms at high iGBA(65-90 Hz), and the interaction between group and race in the 200 ms - 300 ms window. To depressed participants, average high iGBA between 200 ms - 300 ms for other-race faces was larger than that for own race faces, while which didn´t happened to the normal controls. In summary we suppose that race-effect did affect the iGBA of the depressed participants while they performing emotion tasks, especially the negative ones.