The influence of stimulus onset asynchrony on neuronal suppressive phenomenon in face processing: An event-related potential study

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 (200ms, 400ms & 600ms) 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.