A theoretical investigation of reference frames for the planning of speech movements.

Abstract

Does the speech motor control system utilize invariant vocal tract shape targets of any kind when producing phonemes? We present a four-part theoretical treatment favoring models whose only invariant targets are auditory perceptual targets over models that posit invariant constriction targets. When combined with earlier theoretical and experimental results (Guenther, 1995a,b; Perkell eta!., 1993; Savariaux et a!., 1995a,b), our hypothesis is that, for vowels and semi-vowels at least, the only invariant targets of the speech production process are multidimensional regions in auditory perceptual space. These auditory perceptual target regions are hypothesized to arise during development as an emergent property of neural map formation in the auditory system (Guenther and Gjaja, 1996), as evidenced by the perceptual magnet effect. Furthermore, speech movements are planned as trajectories in auditory perceptual space. These trajectories are then mapped into articulator movements through a neural mapping that allows motor equivalent variability in constriction locations and degrees when needed, but maintains approximate constriction invariance for a given sound in most instances. These hypotheses are illustrated and substantiated using computer simulations of the DIVA model of speech acquisition and production. Finally, we pose several difficult challenges to proponents of constriction theories based on this theoretical treatment. Speech reference frames

Invariance and variability in the production of the height feature in French vowels

“…The first is that the stability of F1 values per se may play a role in mastering the French vowel system. This may be compatible with auditory theories of speech production, whereby speech targets are directly specified in auditory terms (Perkell et al, 1997(Perkell et al, , 2004, possibly through articulatory-auditory maps and learned inversion mechanisms (Bailly, 1997;Guenther, 1995;Guenther et al, 1998).…”

The role of the basal ganglia and cerebellum in language processing

“…The motor theory of speech is consistent with studies showing that monkeys discharge the same neurons in motor cortex both when a sound is perceived and when it is executed (Kohler et al, 2002) and with studies showing that humans activate the same brain regions in motor cortex both when observing actions and when listening to action sentences (Tettamanti et al, 2005a). In their DIVA model speech acquisition and production, Guenther and colleagues have also argued that auditory cortex is not only involved in speech perception, but is also involved in planning movement trajectories based on acoustic and orosensory feedback as well as an efference copy of the motor command (Guenther et al, 1998;Nieto-Castanon et al, 2005). Based on this research, one would predict that both the superior temporal cortex and inferior frontal gyrus are involved articulatory planning and control.…”

Neural mechanisms underlying auditory feedback control of speech

“…The DIVA model of speech production (Guenther et al, 1998;Guenther et al, 2006) is a quantitatively defined neuroanatomical model that provides a parsimonious account of how auditory feedback is used for both feedback control and for tuning feedforward commands. According to the model, feedforward and feedback commands are combined in primary motor cortex to produce the overall muscle commands for the speech articulators.…”