Joint attention and brain functional connectivity in infants and toddlers

Initiating joint attention (IJA), the behavioral instigation of coordinated focus of 2 people on an object, emerges over the first 2 years of life and supports social-communicative functioning related to the healthy development of aspects of language, empathy, and theory ofmind. Deficits in IJA provide strong early indicators for autism spectrumdisorder, and therapies targeting joint attention have shown tremendous promise. However, the brain systems underlying IJA in early childhood are poorly understood, due in part to significantmethodological challenges in imaging localized brain function that supports social behaviors during the first 2 years of life. Herein, we showthat the functional organization of the brain is intimately related to the emergence of IJA using functional connectivitymagnetic resonance imaging and dimensional behavioral assessments in a large semilongitudinal cohort of infants and toddlers. In particular, though functional connections spanning the brain are involved in IJA, the strongest brain-behavior associations clusterwithin connections between a small subset of functional brain networks; namely between the visual network and dorsal attention network and between the visual network and posterior cingulate aspects of the defaultmode network. These observationsmark the earliest known description of how functional brain systems underlie a burgeoning fundamental social behavior,may help improve the design of targeted therapies for neurodevelopmental disorders, and,more generally, elucidate physiologicalmechanisms essential to healthy social behavior development.