The influence of stimulus onset asynchrony on neuronal suppressive phenomenon in face processing: an event-related...

It has been reported that if two sensory stimuli are presented consecutively with stimulus onset asynchrony (SOA) of as short as several hundreds of milliseconds, the neural activity, elicited by the second stimulus, in the stimulus-sensitive area will be inhibited, say, suppressive phenomenon. Using a paired-stimulus paradigm, in which two visual stimuli were successively presented, we investigated the influence of SOA (200 ms, 400 ms & 600 ms) on suppressive phenomenon in face processing. Twelve subjects were asked to passively view randomly ordered paired stimuli and single stimuli, while their event-related potentials (ERPs) were recorded simultaneously. To evaluate the suppression, we compared the ERPs elicited by the second face stimulus of the paired stimuli with that elicited by the single face stimulus. It was found that, comparing with the ERPs elicited by single faces, in all three SOA conditions, the ERPs elicited by the second face stimulus of the intra-category trials (face_face trials) were more suppressed than those of the inter-category trials (blank_face and building_face trials) in both occipitotemporal and frontal regions. We surmised that these results might support a "domain specific" theory, which suggested that visual processing of faces and non-face objects involve separate and specialized networks in the ventro-lateral temporal cortex. Interestingly, for the face_face trials, as the SOA increased, the ERP suppression in the frontal region diminished gradually. Such phenomenon might be due to the lasting effect of semantic processing for the first face stimulus.