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Abstract:
Intonation—the modulation of pitch in speech—is a crucial aspect of language that is processed in right-hemispheric regions, beyond the classical left-hemispheric language network. Whether or not this notion generalises across languages remains, however, unclear. Particularly, little is known about intonation in tonal languages, in which pitch not only serves intonation but also expresses meaning via lexical tones. The talk will present two fMRI studies that addressed this dual linguistic function of pitch and explored (i) how intonation is processed in Mandarin Chinese, (ii) how this compares to tone, and (iii) whether or not this differs between tonal and non-tonal language speakers.
Mandarin and German native speakers were presented with mono-syllabic Mandarin words that gradually varied along three acoustic continua: in intonation (from question to statement), in tone (from tone 2 to tone 4), or in voice gender (from male to female). Participants were asked to categorise these stimuli along each of the three dimensions in two-alternative forced-choice tasks, in separate task blocks, while functional MR images were acquired with a 3T Magnetom Prisma scanner.
Brain activity was systematically compared between the three tasks, between stimuli along the continua within each task, and between groups, complemented by a functional connectivity analysis of frontal seed regions. These combined analyses converge on three main findings: First, bilateral fronto-temporal and left parietal regions, as well as enhanced left frontal to bilateral temporal connectivity supported successful intonation categorisation in Mandarin speakers. Second, tone categorisation largely overlapped with intonation processing in bilateral superior temporal and left parietal regions, but evoked significantly less right frontal activity than intonation in Mandarin speakers. Finally, considerable commonalities were found in the neural implementation of intonation processing in both groups, while evidence for semantic processing of tone in bilateral temporo-parietal regions was only found in Mandarin speakers.
Altogether, the data suggest that intonation processing in Mandarin relies on general auditory, phonological, and controlled prosodic labelling processes in bilateral large-scale networks that are similar across speakers of tonal and non-tonal languages. Tone processing shares some of these processes, but with stronger left-lateralisation and additional recruitment of lexico-semantic processes in Mandarin speakers only. These results broaden our current knowledge about the processing of dynamic pitch cues in speech by taking linguistic diversity into account.
