Enhanced pitch centering in individuals with laryngeal dystonia

Laryngeal dystonia (LD) is a neurological voice disorder marked by strained voice quality, pitch instability, and sudden voice breaks, yet the mechanisms underlying impaired vocal control are poorly understood. One key process, known as pitch centering, reflects the central nervous system's ability to correct early pitch deviations during an utterance by converging toward an intended target. While pitch centering provides a sensitive window into the neural control of spontaneous speech, it remains unexamined in patients with LD and is presumed to contribute to disordered regulation of voice production.

Here, we examined pitch centering in 24 individuals with LD [adductor LD (n = 20), abductor LD (n = 3), or both (n = 1)] compared to 29 healthy controls. The primary outcome measures were: (1) Pitch centering and (2) Pitch movement. Pitch centering was defined as the difference in the absolute values of initial (0-50 ms) and mid-trial (150-200 ms) pitch. Positive values (centering > 0) indicated a shift toward the median pitch defined as centering trials. Pitch movement was defined as the difference between mid-trial and initial pitch. In a subset of trials, we observed negative values of centering reflecting movement away from intended pitch targets, which we defined as anticentering trials. An additional subset of trials was defined as overshoot trials, instances where the normalized pitch movement crosses the median pitch at mid-trial.

Initial pitch deviation (p < 0.0001) and pitch movement magnitude (p < 0.0001) were significantly greater in individuals with LD compared to controls across all trials. Importantly, individuals with LD exhibited more pronounced centering responses compared to controls, with greater centering magnitude observed by a significant group-by-tercile interaction (p = 0.028). Individuals with LD and controls showed similar distributions of centering and anticentering trial types. However, LD patients exhibited significantly greater centering magnitude compared to controls across each trial type.

These findings offer valuable insights into speech motor and predictive control processes in LD, with potential implications for clinical assessment and treatment strategies aimed at improving patient quality of life.