Effects of vocal training on voluntary responses to pitch-shifted voice auditory feedback

Abstract

Control of voice fundamental frequency (F0) relies on the interaction between various forms of sensory feedback and neural motor control mechanisms. Several studies have shown that unexpected changes in pitch in the auditory feedback lead to reflexive compensatory vocal responses. We examined voluntary vocal responses to unpredictable perturbations in pitch auditory feedback. Ten subjects were trained over a five-day period to change their voice F0 in the opposite direction to the pitch-shifted feedback (±100 cents, 1000 ms) and 10 in the same direction as the feedback. Results showed that responses that followed the stimulus direction had significantly shorter latencies (200 ms) than opposing responses (324 ms). The reduced latency of the following responses suggests a switch from a feedback to a feedforward control strategy. The feedback strategy requires monitoring feedback and correcting for errors between the feedback signal and the intended vocal goal. The feedforward strategy relies less on auditory feedback and more on an internal model of the desired vocal pitch goal. Furthermore, feedback systems generally are slower than feedforward strategies, which would explain the shorter latencies of the responses that followed the stimulus direction. Results of this study will be discussed in terms of the differing strategies that may be used in various vocal contexts.