A THEORETICAL INVESTIGATION OF REFERENCE FRAMES FOR THE PLANNING OF SPEECH MOVEMENTS

Does the speech motor control system use invariant vocal tract shape t argets when producing vowels and semivowels? A 4-part theoretical trea tment favoring models whose only invariant targets are regions in audi tory perceptual space over models that posit invariant constriction ta rgets is presented. Auditory target regions are hypothesized to arise during development as an emergent property of neural map formation in the auditory system. Furthermore, speech movements are planned as traj ectories in auditory perceptual space. These trajectories are then map ped into articulator movements through a neural mapping that allows mo tor equivalent variability in constriction locations and degrees when needed. These hypotheses are illustrated using computer simulations of the DIVA model of speech acquisition and production. Finally, several difficult challenges to proponents of constriction theories based on this theoretical treatment are posed.