Sensorimotor adaptation to perturbations of vowel acoustics and is relation to perception

Abstract

The overall goal of this dissertation was to study the auditory component of feedback control in speech production. The first study investigated 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. These results indicated that subjects demonstrate compensatory formant shifts in their speech. This compensation was maintained when auditory feedback was masked by noise. The second study investigated perceptual discrimination of vowel stimuli differing in F frequency, using the same subjects as in the SA studies. This study showed that the extent of adaptation was positively correlated with subject auditory acuity. The last study consisted of a series of simulations of SA experiments using a model which describes the motor planning and control of human speech by the brain; these simulations showed that the model can account for several properties of adaptation as measured from the human subjects.

(cont.) The findings in this dissertation support the idea that phonemic speech movements are planned as goal regions in an auditory space, and that mappings between this auditory space and the speech motor plan are adaptable. Moreover, the size of these goal regions-as reflected in speaker auditory acuity-influences the degree to which speakers adapt to errors in auditory feedback.