The role of auditory feedback in speech motor control was explored in three related experiments. Experiment 1 investigated auditory sensorimotor adaptation: the process by which speakers alter their speech production to compensate for perturbations of auditory feedback. When the first formant frequency (F1) was shifted in the feedback heard by subjects as they produced vowels in consonant-vowel-consonant (CVC) words, the subjects' vowels demonstrated compensatory formant shifts that were maintained when auditory feedback was subsequently masked by noise-evidence of adaptation. Experiment 2 investigated auditory discrimination of synthetic vowel stimuli differing in F1 frequency, using the same subjects. Those with more acute F1 discrimination had compensated more to F1 perturbation. Experiment 3 consisted of simulations with the directions into velocities of articulators model of speech motor planning, which showed that the model can account for key aspects of compensation. In the model, movement goals for vowels are regions in auditory space; perturbation of auditory feedback invokes auditory feedback control mechanisms that correct for the perturbation, which in turn causes updating of feedforward commands to incorporate these corrections. The relation between speaker acuity and amount of compensation to auditory perturbation is mediated by the size of speakers' auditory goal regions, with more acute speakers having smaller goal regions.

The goal of this research is to study the auditory component of feedback control in speech production. This experiment investigates auditory sensorimotor adaptation (SA) as it relates to speech production: the process by which speakers alter their speech production in order to compensate for perturbations of their normal auditory feedback. Specifically, the first formant frequency (F1) was shifted in the auditory feedback heard by naive adult subjects as they produced vowels in single syllable words. Initial results indicate that subjects demonstrate compensatory formant shifts in their speech. This compensation was also present after training when acoustic feedback was masked by noise. This suggests that internal models used in the control of speech movements can be constantly updated by auditory feedback. These results in voiced speech are consistent with results from Houde and Jordan [Science 279, 1213–1216 (1998)], which demonstrated SA in whispered speech. A second study, currently underway, investigates perceptual discrimination of vowel stimuli differing in F1 frequency, using the same subjects as in the SA studies. Cross-subject relations between discrimination scores and extent of compensation will be presented and discussed. [Work supported by NIDCD Grant R01-DC01925.]

The goal of this research is to study the auditory component of feedback control in speech production. This experiment investigates auditory sensorimotor adaptation (SA) as it relates to speech production: the process by which speakers alter their speech production in order to compensate for perturbations of normal auditory feedback. Specifically, the first formant frequency (F1) was shifted in the auditory feedback heard by naive adult subjects as they produced vowels in single syllable words. Results presented previously indicate that the subjects demonstrate compensatory formant shifts in their speech. The current study investigates the relationship between compensatory adaptation and speaker perceptual acuity. Subjects from the SA study were tested for their ability to discriminate vowel tokens differing in F1 frequency. Preliminary results indicate that subjects with greater perceptual acuity also demonstrated greater ability to adapt, with a significant cross-subject correlation (p less than 0.05). The relation between these experimental findings and DIVA, a neurocomputational model of speech motor planning by the brain, will also be discussed. [Work supported by NIDCD Grant R01-DC01925.]