Neural mechanisms underpinning Emotional Body Language comprehension: eye tracking and EEG studies.

To date, most investigations in the field of affective neuroscience mainly focused on the processing of facial expressions, overlooking the exploration of emotional body language (EBL), its capability to express our emotions notwithstanding. Considering the lack of previous eye-tracking studies focused on the visual mechanisms subtending visual exploration of bodies and EBL, the aim of our first study was to investigate the patterns of visual exploration during the observation of facial and bodily expressions, clarifying the characteristics of the visual mechanisms during Emotional Body Language processing, in order to consider its importance for the recognition of emotions and intentions of others. To this purpose, we recorded eye movements during an emotion categorization task of facial and bodily expressions depicting three emotional conditions (neutral, happiness and sadness). Specifically, we focused our analyses on the number and duration of fixations directed to specific Areas of Interest –AOIs, defined for faces (forehead, corrugator, eye right, eye left, nose, mouth) and bodies (upper left, upper right, hand left, hand right, lower left, lower right, and head). Considering faces, results showed that participants made more and longer fixations to the eyes and the nose. Moreover, they looked at the region of the mouth directing to it a number of fixations in-between eyes and nose on a side, and forehead and corrugator on the other. These results suggest how participants adopted a holistic viewing strategy, focusing their attention on the salient facial features (eyes, nose and then mouth) and integrating them in a whole representation of the face. With respect to faces, our results suggest the presence of a different exploration mechanism during bodies’ observation, likely based on the spatial relations among different body parts. Moreover, with bodies we found an interesting left-side bias indexed by the significant difference between the left and the right upper part of the body, with the left upper part being different than all the other AOIs. It is worth nothing that, apart the upper parts of the body, the other focused region was the left hand. Considering the few number of studies which explored the visual mechanisms of bodies exploration, these results could be considered as novel seeds to develop future studies in the field. Bearing in mind that few electrophysiological studies investigated the time course and the neural correlates of EBL, and even less investigated the integration of face and body emotion-related information, we used face and body stimuli validated during our first study (see above), to conduct an original ERP study. The aim of the present study was to investigate both the time course and the neural correlates underlying the integration of affective information conveyed by faces and bodies. We analysed EEG activities evoked during the judgment of the emotional congruence between stimuli belonging to the same category (face-face or body-body), and between stimuli belonging to different categories (face-body or body-face). Our results showed that incongruent stimuli elicited a modulation of the N400 in all comparisons except for body-face condition. This modulation was mainly detected in the Middle Temporal Gyrus, indexing the access to the meaning storage system, and within regions related to the mirror mechanism, suggesting the activation of Embodied Simulation mechanisms allowing a direct match between the emotional facial and bodily posture observed and executed, thus allowing the correct interpretation of the emotion conveyed by facial expressions and bodily postures themselves. More specifically, while the perception of incongruent facial expressions activates somatosensory-related representations, incongruent emotional body postures also require the activation of motor and premotor representations, suggesting a strict link between emotion and action.