Project Summary Successful transition of healthy infants from breast- or bottle-feeding to textured foods requires the development of complex neuromuscular control. This transition must also occur within the context of rapid growth and development and increased nutritional demands. To initiate this process, complementary foods are typically introduced by 4-6 months of age and continue throughout early childhood. Delaying the introduction of complementary foods past 10 months of age places an otherwise healthy child at risk for persistent feeding problems to develop well into the school-age years. This suggests that prolonged liquid diets fundamentally alter feeding performance and the underlying oral and pharyngeal function and coordination. Currently, however, limited data is available on precisely what rehabilitation strategy would be best to implement if this critical window of oral sensorimotor development has passed. Our limited understanding is due, in part, to human subject research protections in place for healthy infants and children when examining the swallow during feeding and to their relatively slow growth rates which make longitudinal studies infeasible. The proposed work will determine whether feeding performance and its underlying physiology and biomechanics can be recovered following long-term use of a texture-modified diet during the critical periods of growth and oral sensorimotor maturation in an animal model. This project will compare feeding and swallow-respiratory coupling performance outcomes for animals reared on a texture-modified diet during early maturation and then transitioned to textured foods using one of two rehabilitation strategies: direct transition or progressive transition. The outcomes of these two rehabilitation strategies will be compared to normally-weaned age- matched control animals (Specific Aim 1). This project will also examine the coordination of oral (jaw and tongue) and hyolaryngeal movements and their motor control during feeding in each group (direct transition, progressive transition, controls) (Specific Aim 2). Synchronized high speed biplanar fluoroscopy, electromyography, and respiration data over 4 months in infant, juvenile, and subadult animals will provide sequence- and cycle-level analyses across critical developmental stages. Results will enable us to tease apart the relationship between growth and development, function, and performance as animals transition from a liquid to a solid diet after critical windows of oral development have closed. This research is essential for optimizing specific rehabilitation strategies for healthy infants who struggle to accept complementary foods. This research also lays the groundwork for treating other populations such as healthy preterm infants and children who present with underlying conditions affecting oropharyngeal coordination that complicate weaning and the successful transition to solid foods.