Crowd Facial Expressions In Fast Periodic Visual Stimulation

It is important for people’s social life to quickly identify the emotions carried by a group of people.Previous studies have found that people process multiple faces by ensemble coding.Ensemble coding is fast and accurate,but the influences and the neural mechanisms behind it are poorly understood.The study of ensemble coding by electrophysiological has its own difficulties.The present study overcomes these difficulties by using the Fast Periodic Visual Stimulation paradigm(FPVS)and investigate the ensemble coding of emotional faces.Experiment 1 explores whether crowd faces can be studied by FPVS paradigm.The study was divided into three conditions: six faces with changes in emotion;three faces with changes in emotion and the group with no regular changes,and inverted faces were set as the control condition.It was found that the paradigm was able to capture the changes in crowd face emotions that changed,and the subjects’ coding of group emotions was automatic,but failed to use all six faces.Experiment 2 controlled for subjects’ tasks,divided into a direct task condition and an indirect task condition,and found that the amplitude of oddball frequency was significantly greater in the direct task condition than in the indirect condition,indicating the modulation of ensemble coding by attentional resources.The results also revealed that subjects encoded crowd faces with similar patterns of neural activity to those encoding single face,and identified brain regions that may be associated with ensemble coding ability.In summary,this study used the FPVS paradigm to study crowd face encoding,found that crowd face encoding is automatic but influenced by attentional resources,and revealed the neural mechanisms underlying of crowd face encoding.