Thus, synesthesia is a phenomenon which features increased multimodal integration not ‘across the board’ but only in a restricted fashion, that is, for the inducer–concurrent coupling. First, with regard to the McGurk illusion, successful integration of visual and auditory stimuli leads to a specific illusionary percept. Speech perception thus draws on both, auditory and visual information in case visual information is available. Recent research shows that brain

regions that are usually associated with relatively ‘late’, high level processes are implied in this illusion (Jones & Callan, 2003). In particular the left posterior superior temporal sulcus (STS) and adjacent brain areas have been found in relation to the McGurk illusion (Nath & Beauchamp,

2012; Szycik, Stadler, Tempelmann, & Münte, 2012). The STS has also been found in studies Cobimetinib manufacturer investigating other aspects of audiovisual speech perception (Szycik, Tausche, & Munte, 2008; Wright, Pelphrey, Allison, McKeown, & McCarthy, 2003). Another region important for audiovisual integration is the inferior frontal gyrus (IFG; Ojanen et al., 2005; Szycik, Jansma, & Munte, 2009). The interplay of these ‘late’ regions has been sketched by the audiovisual-motor model of speech perception (Skipper, van Wassenhove, Nusbaum, selleck inhibitor & Small, 2007). As synesthetic experience has also been suggested to be driven by higher level processes such as attention, semantic information or feature binding (Dixon et al., 2006; Esterman et al., 2006; Mattingley, Payne, & Rich, 2006; Mattingley et al., 2001), the McGurk illusion appears to be a good test case to investigate synesthesia. So far, however, only a single publication has dealt with the McGurk illusion in synesthesia (Bargary et al., 2009). Bargary et al. argued that synesthetic experience is a relatively late process. They focused on the perceptual processes in synesthesia after audiovisual fusion happened using audiovisual incongruent whole word stimulation. They were able to show that concurrent colours induced by

spoken words are related to what is perceived 上海皓元医药股份有限公司 rather than to the auditory input. In contrast with Bargary et al. this study focused on the question whether susceptibility to the McGurk illusion is altered in synesthesia compared with non-synesthetic participants. Surprisingly, a reduced susceptibility to the illusion was revealed which suggests reduced audiovisual integration except for the specific inducer–concurrent pairing. One limitation to this study could be the fact that for the Mc Gurk experiment 28 audiovisual incongruent (illusory) stimuli and 12 audiovisual congruent stimuli serving as control were used. Thus, there was considerable imbalance in the design between the answer categories. I might be asked whether the group difference found in our experiment could be due to a different susceptibility of synesthesia subjects to such a design imbalance.