Arousal effect on emotional face comprehension: frequency band changes in different time intervals.

The study aimed to explore the modulation of frequency bands (delta, theta, alpha-1 and alpha-2, and gamma) in response to emotional face within different post-stimulus time intervals (50-450 ms). Twenty adults looked at emotional (happy, sad, angry, fearful) or neutral faces. EEG results showed that motivational significance of face can modulate frequency bands, specifically for theta and gamma. Moreover, gamma can be varied related to degree of arousing feature (high or low) of facial expression. As a function of time, ANOVA and regression analysis revealed that emotional discrimination by gamma and theta is observable mainly within 150-250 time interval and, as revealed also by coherence analysis, that it is more distributed on the anterior-right (theta) or right (gamma) side of the scalp for the emotional stimuli, whereas delta is maximally increased within 250-350 interval and it is more posteriorly (parietal site) distributed for all the stimulus type. We proposed that band modulations respond to variations in processing emotional face, and, whereas delta reflects updating of the stimulus, and theta responds to the emotional significance of face, gamma reflects differences in the arousing power of facial expression.