The exploration of underlying pathophysiology of speech disorders is hampered by the limitations in quantitative assessment of speech production. Current assessments are driven by measures that couple underlying processes of speech production with mechanisms that compensate for speech deficits. We propose a multifactorial approach to decouple these effects and examine underlying processes of speech motor control. In study 1 we conducted a sensorimotor characterization of speech motor control via altered sensory feedback techniques. We applied these measures to investigate effects of dopaminergic medication on laryngeal and articulatory motor control mechanisms in persons with Parkinson’s disease (PwPD). The study outcomes provide preliminary indication that dopaminergic medication may have a differential effect on laryngeal sensorimotor function in PwPD, with a normalization (reduction of atypically large responses) of auditory reflexive responses and an exacerbation (further reduction of atypically small responses) of auditory adaptive responses. The study outcomes also provide insight into the differential effects of dopaminergic medication on laryngeal and articulatory speech subsystems in PwPD. We hope the outcomes will eventually serve as a basis for designing better therapeutics focused on ameliorating voice and speech dysfunctions in PwPD. In study 2 we investigated laryngeal motor control in a population of individuals with and without hyperfunctional voice disorders (HVDs) using three different laryngeal kinematic measures extracted via high-speed video endoscopy techniques. We applied these measures to investigate differential effects of laryngeal tension, movement variability, and movement asymmetry present in individuals with HVDs. Results indicate that individuals with HVDs exhibit statistically significantly higher kinematic stiffness, spatiotemporal indices, and asymmetry indices across rate and effort conditions compared to controls, indicating higher laryngeal tension, production variability, and movement asymmetry. Laryngeal kinematics suggest differing underlying motor control strategies in individuals with HVD relative to controls, which may inform better understanding of the etiology of HVDs. The study outcomes also provide insight into the ability of laryngeal kinematics to differentiate underlying motor control strategies in individuals with various voice disorders with neurological and physiological pathophysiology that could provide crucial insight to guide future clinical intervention. In study 3, a novel neurocomputational model was developed, combining an established neurological framework of speech motor control, with a physics based vocal fold model. This numerical model decouples the neurological and physiological aspects of laryngeal motor control to provide important directions in expanding the understanding of the underlying pathophysiology of laryngeal motor control in PD and HVDs. The model has demonstrated capability to simulate different modes of laryngeal motor control, ranging from short-term (i.e., reflexive) and long-term (i.e., adaptive) auditory feedback paradigms, to generating prosodic contours in speech. LaDIVA can be used to expand the understanding of the physiology of human phonation to enable, for the first time, the investigation of causal effects of neural motor control in the fine structure of the vocal signal. / 2025-02-20T00:00:00Z

Infant visual attention develops rapidly over the first year of life, significantly altering the way infants respond to peripheral visual events. Here we present data from 5-, 7- and 10-month-old infants using the Infant Orienting With Attention (IOWA) task, designed to capture developmental changes in visual spatial attention and saccade planning. Results indicate rapid development of spatial attention and visual response competition between 5 and 10 months. We use a dynamic neural field (DNF) model to link behavioral findings to neural population activity, providing a possible mechanistic explanation for observed developmental changes. Together, the behavioral and model simulation results provide new insights into the specific mechanisms that underlie spatial cueing effects, visual competition, and visual interference in infancy.