Project Summary The prevalance rate of autism spectrum disorder (ASD) is currently 1 out of 59 individuals (CDC, 2018). The current research proposal aims to introduce a new approach for characterization of ASD neurobiology inspired by computational neuroscience that relies on measures of brain signal variability. Previous research in typical individuals has shown that increased brain signal variability is more prevelant in younger individuals and those who perform better on tasks of flexible cognition. This makes brain signal variability a promising new measure of development and flexible cognition that can be used to investigate the neurobiology of ASD and associated inflexible behaviors that characterize the disorder (i.e., restrictive and repetitive behaviors). The current study will have two major goals: 1) identify differences in brain signal variability across development between individuals with and without a diagnosis of ASD, and 2) identify relationships between brain signal variability and restricted and repetitive behaviors in individuals with a diagnosis of ASD using a categorical approach, and in individuals with and without a diagnosis of ASD using a dimensional approach. This proposal aims to further the Interagency Autism Coordinating Committee?s strategic plan of understanding the neural circuitry underlying brain function in ASD. The results will help to create more sophisticated models of ASD neurobiology that incorporate multiple imaging measures of brain function. In turn, more sophisticated models of ASD neurobiology will help to guide and assess behavioral interventions aimed at improving the quality of life of individuals diagnosed with ASD.