Emotions in Motion: Processing of Dynamic and Static Facial Expressions of Happiness and Disgust Investigated by FMRI and EEG

Abstract

The aim of the present dissertation was to reveal the spatio-temporal processing of dynamic and static facial expressions of happiness and disgust investigated by fMRI and EEG. The fMRI study resulted in stronger and more widespread activation patterns for the processing of happy and disgusted compared to neutral faces in, e.g., the amygdala, inferior frontal, occipital, superior temporal regions and the fusiform gyrus (FuG). The time course of static and dynamic emotional face processing was investigated with a high-resolution EEG using the same study design. ERP data of static facial expressions indicated a stronger deflection of the N170 in right-lateralized posterior electrode sites for emotional compared to neutral stimuli. Both, static and dynamic facial expressions showed a sustained positivity (LPP) over centro-parietal areas for emotional compared to neutral. Among other, a constrained regional source model of static stimuli revealed an emotional modulation of the insula with an enhancement of activity of disgust compared to neutral stimuli between 300 and 350 ms. Source power in dynamic stimuli yielded an enhancement of left superior temporal gyrus (STG) (200 ms), left precentral gyrus (250 ms, 400ms), and right inferior frontal gyrus (300, 450 ms) for disgust, and an enhancement of left cuneus (200 ms, 500 ms), left FuG (250ms), inferior frontal gyrus (250 ms), and right medial frontal gyrus (400 ms) for the happy compared to the neutral faces.The results of the study support the view that a combined fMRI and EEG approach of studying emotional perception enhances our knowledge about the time course of activation of different sources and reveals sources which have not reached significance in fMRI. The modality aspects of static compared to dynamic stimuli are discussed as well as functional aspects of sources in the context of e.g. disgust perception (insula), biological motion (STG), and facial identity perception (FuG).