Project Summary Children with cerebral palsy (CP) have a range of communication ability profiles. The majority have the speech motor disorder, dysarthria, which almost always results in reduced speech intelligibility. Heterogeneity among children with CP poses challenges for the study of speech and language development, necessitating the use of prospective longitudinal methods wherein each child can serve as their own control. We began such work 15 years ago, following 90 children with CP, with the long-term goal of generating theoretically driven, empirically validated, longitudinal models of speech and language development that can be used to predict outcomes, guide treatment decisions, and test interventions for children with CP. To date, we have developed and validated prospective, data-driven models of speech and language development, and created a clinical speech-language profile group paradigm for children with CP. Our research has resulted in the first published growth curves for speech intelligibility, and language comprehension, leading to the ability to predict later speech and language outcomes with a high level of accuracy based on performance at only 3 years of age. Our data have revealed that children with CP have a protracted developmental timeframe for the acquisition of speech, with many still making intelligibility improvements through the age of 15 years. Despite major gains in our understanding of speech and language development and in the application of this knowledge to clinical decision making, progress is limited by two key barriers, addressed in this application: a.) The upper limits of speech and language development after 15 years of age in CP have not been studied; therefore, we are unable to generate comprehensive growth models that encompass all of development and include young adult outcomes. b.) Treatment options for improving speech intelligibility in children with CP are limited and have primarily focused on remediating speech subsystem deficits. Interventions focused on using augmentative and alternative communication (AAC) strategies to supplement speech have not been examined in children, but findings from adult CP studies are promising. In this renewal, we will collect new longitudinal data on our existing cohort of youth with CP through the age of 20 years. We will also study 100 new children with CP in a Phase I speech supplementation intervention study. Aims are: 1.)To quantify longitudinal change in speech and language development between the ages of 2 and 20 years in children with CP. 2.)To develop and test basic elements of a speech supplementation intervention to improve intelligibility in children with CP (Phase I behavioral clinical trial). This work will complete the development and validation of longitudinal models of speech and language growth in children with CP to 20 years of age. Results will enable the prediction of outcomes for children with CP between 2 and 20 years, which will have direct ...