When audio and visual stimuli are presented very close to each other in time, different perceptual effects regarding the synchronous/asynchronous perception is depending on which of the two is presented first. The mechanism underlying this asymmetric phenomenon and the time-course according to which asynchronous or synchronous perceptual judgments are still under debate. To address these questions, we combined an audio-visual simultaneity judgment task and EEG. In line with past studies, our results also showed an asymmetric phenomenon where the VA ordering results in a wider time window in which the stimuli are judged to be synchronous/asychrouous than the AV condition. Intriguingly, N1 and P1 amplitudes in response to the first stimulus were found to be higher during AV trials in which participants reported perceiving asynchronous audio and visual stimuli. These results point to possibility that the some information contained in intrinsic activity alternated perceptual experience and affected the subsequent behavioral performance even subjects have not perceived the first stimulus.