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Abstract:
Prosody is a language feature that enables us to express meaningful intentions or emotions by means of vocal tone and rhythm variations. Recent neural models of prosody comprehension proposed that a right hemispheric network is specialized for the processing of linguistic prosody, and that it is divided into two pathways with a common core area: posterior superior temporal sulcus (pSTS). The present study investigated whether right pSTS provides a crucial brain basis for prosody perception, in a paradigm combining fMRI with disruptive inhibitory transcranial magnetic stimulation. 29 participants executed prosody and phoneme categorization tasks in the MRI scanner, after application of TMS to one of three different stimulation sites: right pSTS, left pSTS or vertex. The stimulus material consisted in recordings of single words, morphed along phoneme (between ”Bear” and Pear”) and prosody (between question/statement) continua. Stimuli were identical for both tasks, individually selected according to each participant’s perception and were matched for difficulty. The data show that behavioural performance was not affected by TMS, and that according to the imaging data, no decrease of activation was found in the targeted areas after TMS application. No brain area, except for supplementary motor area, was more strongly activated during prosody than phoneme task execution. However, phoneme task induced stronger activation in frontal areas -superior frontal gyrus and middle frontal gyrus- after left pSTS and vertex stimulation, as well as in right angular gyrus after left pSTS stimulation. While the data do not exclude a role of right pSTS in perception of prosodic stimulus features, that may have cancelled out in the present contrasts, the results call for further pitch-wise analyses in order to distinguish between clear and ambiguous prosody perception. Moreover, the results invite the reflection on improving powerful and reliable TMS protocols to study higher-order cognitive processes.
