Intrinsic Functional Connectivity in Attention-Deficit/Hyperactivity Disorder: A Science in Development

Functional magnetic resonance imaging without an explicit task (i.e., resting-state functional magnetic resonance imaging) of individuals with attention-deficit/hyperactivity disorder (ADHD) is growing rapidly. Early studies were unaware of the vulnerability of this method to even minor degrees of head motion, a major concern in the field. Recent efforts are implementing various strategies to address this source of artifact along with a growing set of analytic tools. Availability of the ADHD-200 Consortium data set, a large-scale multisite repository, is facilitating increasingly sophisticated approaches. In parallel, investigators are beginning to explicitly test the replicability of published findings. In this review, we sketch out broad, overarching hypotheses that are being entertained, while noting methodological uncertainties. Current hypotheses implicate the interplay of default, cognitive control (frontoparietal), and attention (dorsal, ventral, salience) networks in ADHD; functional connectivities of reward-related and amygdala-related circuits are also supported as substrates for dimensional aspects of ADHD. Before these can be further specified and definitively tested, we assert the field must take on the challenge of mapping the “topography” of the analytic space (i.e., determining the sensitivities of results to variations in acquisition, analysis, demographic and phenotypic parameters). Doing so with openly available data sets will provide the needed foundation for delineating typical and atypical developmental trajectories of brain structure and function in neurodevelopmental disorders, including ADHD, when applied to large-scale multisite prospective longitudinal studies, such as the forthcoming Adolescent Brain Cognitive Development study.