Autistic brains are distinguished in part by their “functional connectivity” long distance correlations in the neural activity of different brain regions. The meaning of functional connectivity patterns and how they relate to the behavioral phenomena of autism are still unclear, and investigation of functional connectivity mechanisms in humans is not possible. This proposal will address this problem by examining functional connectivity in a rat model of fragile X syndrome, a genetically defined autism spectrum disorder. Brain imaging experiments in animals will be used to characterize the differences between normal and diseased rats. Localized inactivation experiments will then be performed to test whether specific brain regions can account for functional connectivity effects, and to study how connectivity networks depend on the contributions of individual neural structures. This work will advance the study of autism by probing the pathology of an animal model and by suggesting specific neural activity manipulations that could either simulate or potentially reverse the physiological changes that occur in autism disorders.