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

## TL;DR

This study shows how both sides of the brain's posterior middle temporal gyri help control speech when hearing unexpected changes in pitch, with different roles in early and late stages of correction.

## Contribution

The study provides the first causal evidence of bilateral pMTG involvement in vocal feedback control and reveals phase-specific interhemispheric interactions.

## Key findings

- c-TBS over the left, right, or bilateral pMTG reduced vocal compensation magnitudes and shortened latencies.
- Bilateral pMTG stimulation uniquely reduced N1 responses, while P2 responses showed enhanced activity from distinct brain networks.
- The pMTGs show a transition from bilateral coordination in early error detection to unilateral sufficiency in later motor correction.

## Abstract

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.

This study demonstrates the causal roles of the left and right posterior middle temporal gyri in vocal feedback control and reveals a phase‐specific interhemispheric mechanism that transitions from coordinated error detection to independent correction, offering novel neuromodulation strategies for speech rehabilitation.