Attenuation of vocal responses to pitch perturbations during Mandarin speech.

The effect of stimulus timing on vocal responses to pitch-shifted feedback was investigated in different intonation patterns during Mandarin speech production. While speaking a four-word sentence consisting of the high-level tone, where the fundamental frequency (F(0)) of the final word was either increased (question intonation) or slightly falling (statement intonation), pitch-shift stimuli (+/-100 cents, 200 ms duration) were presented at three different times (160, 240, or 340 ms) after vocal onset. Results showed that in the question intonation, response magnitudes (16 cents) were significantly reduced for the 340 ms condition compared to the 160 (26 cents) or 240 (23 cents) ms conditions. No significant differences were found, however, as a function of stimulus timing in the statement intonation. These findings demonstrate that a planned change in F(0) can cause a modulation in the reflexive response to a perturbation in voice pitch feedback and that there is a critical time period during which the response mechanisms are most sensitive to the planning process. These findings suggest an approach for the study of mechanisms involved in the timing of successive words during speech.