title: Exercise-related changes in between-network connectivity in overweight/obese adults.
abstract: Understanding how exercise affects communication across the brain in overweight/obese individuals may provide insight into mechanisms of weight loss and maintenance. In the current study, we examined the effects of a 6-month exercise program in 11 overweight/obese individuals (mean BMI: 33.6±1.4mg/kg(2); mean age: 38.2±3.2years) on integrative brain "hubs," which are areas with high levels of connectivity to multiple large-scale networks thought to play an important role in multimodal integration among brain regions. These integrative hubs were identified with a recently developed between-network connectivity (BNC) metric, using functional magnetic resonance imaging (fMRI). BNC utilizes a multiple regression analysis approach to assess relationships between the time series of large-scale functionally-connected brain networks (identified using independent components analysis) and the time series of each individual voxel in the brain. This approach identifies brain regions with high between-network interaction, i.e., areas with high levels of connectivity to many large-scale networks. Changes in BNC following exercise were determined using paired t-tests, with results considered significant at a whole-brain level if they exceeded a voxel-wise threshold of p<0.01 and cluster-level family-wise error (FWE) correction for multiple comparisons of p<0.05. Following the intervention, BNC in the posterior cingulate cortex (PCC) was significantly reduced (p<0.001). The changes driving the observed effects were explored using Granger causality, finding significant reductions in both outgoing causal flow from the PCC to a number of networks (p<0.05; language network, visual network, sensorimotor network, left executive control network, basal ganglia network, posterior default mode network), in addition to reductions in ingoing causal flow to the PCC from a number of networks (p<0.05; ventral default mode network, language network, sensorimotor network, basal ganglia network). Change in BNC was related to changes in aerobic fitness level (VO2 max; p=0.008) and perceived hunger (Three Factor Eating Questionnaire; p=0.040). Overall, the impact of exercise on communication between large-scale networks may contribute to individual responsivity to exercise.
authors.affiliation: Department of Psychiatry, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, United States. Electronic address: Kristina.Legget@ucdenver.edu.
authors.forename: Kristina T
authors.initials: KT
authors.lastname: Legget
authors.affiliation: Department of Psychiatry, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, United States.
authors.forename: Korey P
authors.initials: KP
authors.lastname: Wylie
authors.affiliation: Division of Endocrinology, Metabolism and Diabetes, Department of Medicine, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, United States; Anschutz Health and Wellness Center, University of Colorado Anschutz Medical Campus, Aurora, CO, United States.
authors.forename: Marc-Andre
authors.initials: MA
authors.lastname: Cornier
authors.affiliation: Division of Endocrinology, Metabolism and Diabetes, Department of Medicine, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, United States; Division of Geriatric Medicine, Department of Medicine, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, United States.
authors.forename: Edward L
authors.initials: EL
authors.lastname: Melanson
authors.affiliation: Department of Psychiatry, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, United States.
authors.forename: Courtnie J
authors.initials: CJ
authors.lastname: Paschall
authors.affiliation: Department of Psychiatry, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, United States; Research Service, VA Medical Center, Denver, CO, United States.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Tregellas
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D001481:Basal Metabolism; D001823:Body Composition; D001921:Brain / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001931:Brain Mapping; D015444:Exercise / Q000502:physiology*; D005260:Female; D006728:Hormones / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008451:Maximal Voluntary Ventilation; D009765:Obesity / Q000000981:diagnostic imaging / Q000503:physiopathology*; D050177:Overweight / Q000000981:diagnostic imaging / Q000503:physiopathology*; D010100:Oxygen / Q000097:blood
chemical_list: D006728:Hormones; D010100:Oxygen
keywords: Between-network connectivity; Default mode network; Exercise; Obesity; Posterior cingulate cortex; fMRI