Modeling sensory preference in speech motor planning

Jean-François Patri (1, 2) , Julien Diard (1) , Pascal Perrier (2)

1 LPNC - Laboratoire de Psychologie et NeuroCognition
2 GIPSA-PCMD - GIPSA - Perception, Contrôle, Multimodalité et Dynamiques de la parole

Speech is a stream of specific sounds performed by gestures of articulators of the vocal tract. The sensory correlates of speech production are therefore both auditory (concerning sounds) and somatosensory (concerning the position and configuration of articulators of the vocal tract). Since sounds are a consequence of speech gestures, these two sensory correlates appear to be redundant in unperturbed conditions. This raises questions about their functional involvement in the monitoring of speech production: is only one useful, and if so, which one? Are they instead both useful, and if so, are they equivalent or complementary? Experimental studies of compensations for auditory and somatosensory perturbations indicate that both types of sensory information are taken into account during speech production. In addition, individual sensory preferences in speech production have been observed: subjects who compensate less for somatosensory perturbations compensate more for auditory perturbations, and vice versa. Our goal is to understand how sensory preferences can operate during speech production and influence it, by using our recently designed Bayesian model of speech motor planning. To our knowledge, models of speech motor control have generally not addressed this issue since they did not systematically evaluate the consequences of variations in the weight of each modality in the specification of the motor goals. In this work, we present extensions of our original Bayesian model of speech motor planning in which speech units are characterized both in auditory and somatosensory terms. We show that sensory preferences can be modeled in two ways. In the first variant, sensory preferences are attributed to the relative precision of sensory regions characterizing speech motor goals. This is inspired from classical models of multisensory fusion for perception. Under this approach, precisions of sensory regions correspond to their tolerance to perturbations: the smaller the region, the higher the precision and the lower the tolerance to perturbations. In other words, subjects who compensate more to auditory than somatosensory perturbations would have auditory target regions smaller than their somatosensory target regions. However, since auditory and somatosensory consequences of speech gestures are highly correlated, why would these motor goal regions differ so considerably?In the second variant of our model, sensory preferences are the consequence of the precision by which the predicted sensory consequences of motor commands are compared to the sensory characterizations of motor goals. We demonstrate that under specific assumptions, our two implementations of sensory preferences are formally equivalent. This reconciles these two approaches and suggests an alternative and original interpretation of sensory preferences.

Domaines: Sciences cognitives

Jean-François Patri, Julien Diard, Pascal Perrier. Modeling sensory preference in speech motor planning. NCM 2017 - 27th Annual Meeting of the Society for Neural Control of Movement, May 2017, Dublin, Ireland. ⟨hal-01614559⟩