Abstract

Synaesthesia is a rare heritable condition in which normal sensory stimulation gives rise to abnormal additional experiences. Many different types of synaesthesia exist; the most common varieties involve perception of a particular colour in response to specific graphemes, musical notes or time-units. Previous work (Barnett et al., in press) has shown that different types of synaesthesia can run in the same family suggesting that a common genetic mechanism underlies all forms of synaesthesia. How exactly synaesthesia arises from its genetic endowment is unknown, but all contemporary models of synaesthesia agree that there is additional communication between certain cortical areas in synaesthetes. These models disagree however, concerning the nature (functional/structural), specificity (unique mechanism/common to us all but enhanced) and location (in relation to the processing hierarchy) of this additional communication or cross-talk. I will present results from a number of audiovisual experiments carried out on synaesthetes examining such issues as the specificity and location of the abnormal cross-talk. For example, do synaesthetes show enhanced communication between the senses in general, reflective of a broader phenotype? Is synaesthesia mediated by lower level sensory information or does it depend on more higher level perceptual processes? These results have implications for neurodevelopmental models of synaesthesia.