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Prosodic and Phonetic Coordination of Speech: fMRI Evidence for Parallel Circuits
Poster Session A, Friday, September 12, 11:00 am - 12:30 pm, Field House
Minkyu Kim1, Oren Poliva2, Chris Naber3, Bradley Buchsbaum4, Connor Mayer1, Caroline Niziolek3, Jonathan Venezia2, Gregory Hickok1; 1University of California, Irvine, 2VA Loma Linda Healthcare System, 3University of Wisconsin–Madison, 4Rotman Research Institute
Human speech production is hypothesized to rely on two parallel hierarchical cortical motor pathways: one for laryngeal control of vocal pitch/prosody and another for supralaryngeal control of phonetic and syllabic sequences. Here, we test this hypothesis using functional magnetic resonance imaging (fMRI). Fifteen adult participants (N = 15; to date) completed two task-based fMRI paradigms. The first aims to differentiate the sub-circuits responsible for pitch modulation and supralaryngeal articulation within the speech production networks, where we compare neural activations during speech repetition tasks (Hickok et al. 2009, J. Neurophysiol.; Rong et al. 2018, PLoS ONE) across stimuli composed of four CV syllables that varied independently along prosodic (pitch) and segmental (non-pitch) dimensions. The second experiment aims to isolate pitch-specific and (non-pitch) segment-specific pathways from broader speech coordination networks by examining neural responses during speech production tasks under Altered Auditory Feedback (AAF; Tourville et al. 2008, Neuroimage; Niziolek & Guenther 2013, J. Neurosci.) that selectively perturbed either pitch or vowel formant frequencies. In both experiments, we aim to delineate the distinct neural circuits involved in coordinating pitch modulation versus segmental (phonetic) articulation. Preliminary analyses reveal a consistent neural association (i) between pitch/prosodic variation and specific regions of the left premotor cortex, particularly area 55b (Glasser et al., 2016), and (ii) between segmental/phonetic variation and classical Broca’s area. These findings support proposed roles of the dorsal region of the premotor cortex in pitch-related processing (Silva et al. 2022, J. Neurosci.; Hickok et al. 2022, Brain) and the ventral region of the premotor cortex in supralaryngeal articulatory control. This work not only deepens the understanding of the neural basis of vocal pitch/prosody and phonetic/syllabic ability but also holds potential implications for clinical interventions in speech and language disorders.
Topic Areas: Speech Motor Control, Language Production