Does temporal adaptation affect multisensory integration?

Abstract

Generally speaking, multisensory integration is more likely to occur when the stimuli are synchronous (Stein and Meredith, 1993). Repeated exposure to temporally offset multisensory stimuli can change the perceived delay between the stimuli so that synchrony is perceived closer to the adapted delay rather than physical synchrony (Fujisaki et al., 2004). If the perception of synchrony is adaptable, might the point (or delay) of maximal integration also be altered after adaptation? Temporal adaptation might be achieved by changing the processing times of the component stimuli (Harrar and Harris, 2008; Navarra et al., 2009), or changing the integration mechanism. In the present study, each participant underwent daily adaptation to either synchronous or asynchronous (auditory lagging by 200 ms, or visual lagging by 60 ms) stimulus pairs. To assess unimodal processing time changes, we measured reactions times (RTs) to audio and visual stimuli after adaptation. In order to assess the effects of adaptation on multisensory integration, we measured RTs to synchronously presented AV stimuli and compared these with the RTs predicted from the Miller’s race model (Miller, 1982) for each participant (Molholm et al., 2004). The results comparing RTs following synchronous and asynchronous adaptation conditions are discussed in the context of perception versus action and current models of multisensory integration. The RTs changed considerably over a period of a week; these patterns are discussed in the context of learning to perceive synchrony.