New results in neuroscience, behavior, and genetics of synesthesia

摘要

Synesthesia is a phenomenon in which stimulation of one sense triggers an experience in another sense. The most common forms produce an automatic perception of color in response to a grapheme or a word, although there are many forms involving various sensory associations with smell, taste, and touch. Synesthesia is thought to occur in at least 1% of the population, and the associations are quantifiable by measuring their consistency within subjects over time. Using data from the online Synesthesia Battery (www.synesthete.org; Eagleman et al, 2007), we have analyzed the forms of synesthesia reported by almost 6,000 synesthetes. Our results indicate that synesthesia forms tend to cluster into five main groups, one of which we term colored sequence synesthesia (CSS). This clustering pattern suggests that synesthetes with one colored sequence (e.g. number-color) are likely to have others (e.g. letter-color, weekday-color, month-color) but unlikely to have a form like music-color. In an effort to elucidate the neural activity underlying CSS, we present neuroimaging data collected while showing synesthetes clips of black and white children's television. Our preliminary data indicate that synesthetes and non-synesthetes process color in anatomically distinct regions. Finally, the genetic mechanisms responsible for synesthesia have been widely debated but remain largely unknown. We present data from our ongoing family linkage analysis, collected from 48 individuals in five large families. Each affected synesthete was verified for CSS using the Synesthesia Battery. Our results implicate a 23MB region on chromosome 16. In sum, we combine data from cluster analyses, neuroimaging studies, and genetic linkage analyses to present a coherent picture of the neural basis of synesthesia, an understanding which will serve as a powerful guide to the normal operations of neural cross-talk and perception.