Control modeling toward understanding articulatory disfluency in autism spectrum disorder

Abstract

Speech control models founded on principles of neuroscience have potential to create powerful clinical tools for personalized medicine and for understanding behavior. We explore two prominent speech control models: Directions into Velocities of Articulators (DIVA) (Guenther, 2006) and Task Dynamics (TD) (Saltzman, 1991) toward an understanding of speech disfluency of autism spectrum disorder (ASD). To introduce perturbations into both systems in the common framework of (Parrrell, 2018), we translate the TD model into MATLAB Simulink. For word stimuli, we compare both models’ acoustic outputs, under the hypothesis that speech impediments in ASD arise from overreliance on delayed sensory feedback (Lin, 2015). For DIVA, the output from a 50ms auditory feedback delay contain increased formant production errors and formant oscillations at about 10Hz, sometimes observed in disfluent ASD cases, but also seen in stuttering (Civier, 2010). The same delay introduced in the proprioceptive and tactile feedback in TD takes 5x the time to settle at the target, creating about 20Hz oscillations in TD articulators. Though neither fully capturing disfluency in ASD, together these models lay the groundwork for a more complete neurocomputational speech control model that can be used to longitudinally track and potentially guide ASD speech therapy.