In a combined psychophysical and electrophysiological study of audio-visual integration and perception of temporal order we employed a spatial AV-TOJ task with bimodal and unimodal conditions, similarly to the study of Zampini et al. (2003). Participants were asked, irrespective of the sensory modality, to report on which side they perceived the onset of the first stimulus. Moreover, to contrast the neuronal correlates of bimodal and unimodal processing, this spatial design allowed us to use in our ERP analysis the term (AV+VA)-(AA+VV) (Gondan et al., 2005). This avoided possible overestimation in case of a third unknown but unspecific factor "C" in all three conditions applying the often used term AV-(A+V).
Our psychophysical analysis confirmed Zampini's (2003) observation that in such a spatial TOJ, the bimodal temporal resolution measured by the just noticeable difference (JND) is smaller (higher JNDs) than the unimodal temporal resolution, especially than the visual. For the bimodal condition, however, we could not find a clear necessity for the visual modality to lead the auditory modality in order to be perceived as simultaneous. Looking on the participant’s level it was rather evident that the results in the bimodal conditions were characterized by high interindividual differences. ERP-correlates will be presented.