The phase analysis of ongoing EEG oscillations under face/object perception

Event-related potentials (ERPs) analysis has been widely used in the cognitive studies due to its good performance in reflecting the time-locked stimulus-related brain activities. However, recent studies have found that the phase coherence of ongoing EEG oscillations is also related to stimulus-related brain activities and could reveal some information (e.g. phase-locked modulation in time-frequency domain) that ERPs could not provide. Here, we used inter-trail phase coherence(ITPC) to analyze the ongoing EEG oscillations under face/object stimuli, which aimed to explore the influence of face/object stimuli on EEG oscillations at various frequency bands (alpha, beta and low frequency gamma). Our preliminary results showed that (1) alpha band has relatively high phase synchronization in the time window of P1-N170-P2 under face/object stimuli; (2) EEG for face stimuli showed higher phase synchronization than object did in the time window of 80-350 ms in alpha band; (3) in low frequency gamma band, faces evoked relatively higher phase synchronization around 170ms than objects did. These results indicated that (1) ITPC, the measure of EEG phase synchronization, could be effectively used in face/object perception to provide oscillatory phase information; (2) the modulation of ITPC value in the alpha band might be more suitable to investigate the face preference EEG activities and locate the time range of the early face perception compared with ERPs; (3) the difference between face and object processing could be reflected in the low frequency gamma band via ITPC values.