Phase-Specific Contributions and Interactions of the Left and Right Posterior Middle Temporal Gyri in Vocal Feedback Control: Evidence From Dual-Site TMS.

The posterior middle temporal gyrus (pMTG) has been implicated in sensorimotor control of speech production, but the causality underlying this relationship remains largely unclear. The present event-related potential study employed dual-site continuous theta burst stimulation (c-TBS) over the left and right pMTGs concurrently to investigate their causal roles and interhemispheric interactions in vocal feedback control. Following bilateral c-TBS, unilateral c-TBS paired with contralateral sham stimulation, or bilateral sham stimulation over the left and right pMTGs, 24 healthy young adults produced sustained vocalizations while exposed to unexpected pitch perturbations (±200 cents) in auditory feedback. Compared to sham stimulation, c-TBS over the left, right, or bilateral pMTG significantly reduced the magnitudes and shortened the latencies of vocal compensations, paralleled by enhanced P2 responses that received contributions from distinct fronto-tempo-parietal networks. In contrast, reduced N1 responses were observed only following bilateral pMTG stimulation. Our findings not only provide the first causal evidence for bilateral pMTG involvement in vocal feedback control but also reveal a phase-specific interhemispheric interaction, transitioning from bilateral coordination during early error detection to unilateral sufficiency during later motor correction. These insights pave new avenues for developing novel multi-site neuromodulation protocols to optimize speech rehabilitation.