Hemispheric specialization of the processing of linguistic pitch contrasts.

摘要

Unlike a nontone language such as English, the pitch pattern of a spoken word in a tone language can determine its meaning. For example, the Mandarin syllable /ma/ can mean 'mother' or 'to scold' depending on changes in pitch (or tone). Recent neuroimaging data suggest that this functional difference induces distinct functional brain organization for pitch perception. In this dissertation, a positron emission tomography experiment was conducted to examine this issue with a wider array of controls. Mandarin speakers and English speakers discriminated Mandarin word pairs differing in tone, English word pairs differing in the same tonal patterns, and English word pairs differing in final consonants. Only when Mandarin subjects discriminated Mandarin did the pitch patterns contrast word meaning. Subjects also passively listened to Mandarin and English. The strongest activation present when Mandarin subjects discriminated Mandarin, as contrasted to passive Mandarin listening, was in left anterior insula, bordering BA 45, inferior to Broca's area. When Mandarin subjects discriminated English pitch and English consonants, a homologous area on the right, but not the left, was strongly active (relative to passive controls). This same area was strongly active and only on the right when English speakers discriminated Mandarin tones, English pitch patterns, and English consonants. There were other more subtle differences amongst groups and tasks, as well as weaker activations in other areas for each active task. Overall, these data confirm that language experience and context affect which brain areas subserve pitch pattern perception.