Auditory-Motor Control of Fundamental Frequency in Essential Vocal Tremor.

Purpose: The purpose of this study was to assess feedforward control of voice in essential vocal tremor (EVT) by measuring adaptive responses to gradual perturbation of the pitch of the auditory feedback and to assess feedback control of voice in EVT by measuring reflexive responses to sudden perturbation of the pitch of the auditory feedback. Method: Ten participants with EVT and 10 age-, sex-, and gender-matched controls produced sustained vowels while the fundamental frequency (fo) of their auditory feedback was gradually perturbed to assess feedforward control and suddenly perturbed to assess feedback control. Acoustical analyses estimated the mean fo of their adaptive and reflexive responses. Participants with EVT also underwent comprehensive auditory, acoustical, physiological, and cognitive assessments to assist with interpretation of their responses to pitch perturbations. Results: Participants with EVT and controls produced compensatory responses to gradual and sudden pitch perturbations. The differences in adaptive and reflexive response magnitudes for participants with EVT and controls were not statistically significant. However, participants with EVT exhibited significantly lower variability in their adaptive responses relative to control participants. There was no apparent pattern in auditory, acoustical, physiological, or cognitive assessment findings that accounted for the differences in adaptive response magnitudes across participants with EVT. Conclusions: These findings indicated that speakers with EVT had typical adaptive and reflexive response magnitudes, suggesting that speakers with EVT may have typical feedforward and feedback control of pitch in EVT. However, the sources of observed differences in the variability of adaptive response magnitudes require further investigation. [ABSTRACT FROM AUTHOR]