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Physical activity and sedentary behaviors have been linked to a variety of general health benefits and problems. However, few studies have examined how physical activity during childhood is related to brain development, with the majority of work to date focusing on cardio-metabolic health. This study examines the association between physical activity and screen time with white matter microstructure in the general pediatric population. In a sample of 2532 children (10.12 ± 0.58 years; 50.04% boys) from the Generation R Study, a population-based cohort in Rotterdam, the Netherlands, we assessed physical activity and screen time using parent-reported questionnaires. Magnetic resonance imaging of white matter microstructure was conducted using diffusion tensor imaging. Total physical activity was positively associated with global fractional anisotropy (β = 0.057, 95% CI = 0.016, 0.098, p = 0.007) and negatively associated with global mean diffusivity (β = -0.079, 95% CI = -0.120, -0.038, p < 0.001), two commonly derived scalar measures of white matter microstructure. Two components of total physical activity, outdoor play and sport participation, were positively associated with global fractional anisotropy (β = 0.041, 95% CI=(0.000, 0.083), p = 0.047; β = 0.053, 95% CI=(0.010, 0.096), p = 0.015, respectively) and inversely associated with global mean diffusivity (β = -0.074, 95% CI= (-0.114, -0.033), p < 0.001; β = -0.043, 95% CI=(-0.086, 0.000), p = 0.049, respectively). No associations were observed between screen time and white matter microstructure (p > 0.05). This study provides new evidence that physical activity is modestly associated with white matter microstructure in children. In contrast, complementing other recent evidence on cognition, screen time was not associated with white matter microstructure. Causal inferences from these modest associations must be interpreted cautiously in the absence of longitudinal data. However, these data still offer a promising avenue for future work to explore to what extent physical activity may promote healthy white matter development., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Early life factors may influence brain and academic outcomes later in life, especially during childhood. Here we investigate the associations of early life factors (i.e., birth weight, birth length, and breastfeeding) with gray matter volume, adjusted for body mass index and cardiorespiratory fitness, and ii) we test whether early-life factor-related differences in gray matter volume are associated with academic performance in overweight/obese children. 96 children with overweight/obesity aged 8-11 years participated. Birth weight, birth length and gestational age were collected from birth records, and breastfeeding practices were asked to parents. T1-weighted images were acquired with a 3.0 T Magnetom Tim Trio system. Academic performance was assessed with the Bateria III Woodcock-Muñoz Tests of Achievement. Whole-brain voxel-wise multiple regressions were used to test the associations of each early life factor with gray matter volume. Higher birth weight and birth length were associated with greater gray matter volume in 9 brain regions including the middle frontal gyrus, rectal gyrus, thalamus, putamen, middle temporal gyrus, lingual gyrus, middle occipital gyrus, calcarine cortex and cerebellum bilaterally (β ranging from 0.361 to 0.539, t ranging from 3.46 to 5.62 and cluster size from 82 to 4478 voxels; p < 0.001); and greater duration of any breastfeeding was associated with greater gray matter volume in 3 regions including the bilateral inferior frontal gyrus and rolandic operculum (β ranging from 0.359 to 0.408, t ranging from 4.01 to 4.32 and cluster size from 64 to 171 voxels; p < 0.001). No associations were found for duration of exclusive breastfeeding. Additionally, none of the gray matter regions that were associated with the early life factors were associated with academic performance (all p > 0.05). Our results demonstrate that birth weight, birth length, and breastfeeding are predictive of gray matter volume of numerous brain structures that are involved in higher order cognition and emotion regulation, but how these results relate to measures of academic achievement remain a matter of speculation., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Cortical thickness and surface area are thought to be genetically unrelated and shaped by independent neurobiological events suggesting that they should be considered separately in morphometric analyses. Although the developmental trajectories of cortical thickness and surface area may differ across brain regions and ages, there is no consensus regarding the relationships of physical fitness with cortical thickness and surface area as well as for its subsequent influence on intelligence. Thus, this study examines: (i) the associations of physical fitness components (i.e., cardiorespiratory fitness, speed-agility and muscular fitness) with overall and regional cortical thickness and surface area; (ii) whether body composition indicators (i.e., body mass index, fat-free mass index and fat mass index) mediate these associations; and (iii) the association of physical fitness and cortical thickness with intelligence in overweight/obese children. A total of 101 overweight/obese children aged 8-11 years were recruited in Granada, Spain. The physical fitness components were assessed following the ALPHA health-related fitness test battery. T1-weighted images were acquired with a 3.0 Tesla Siemens Magnetom Tim Trio system. We used FreeSurfer software version 5.3.0 to assess cortical thickness (mm) and surface area (mm 2 ). The main results showed that cardiorespiratory fitness and speed-agility were related to overall cortical thickness (β = 0.321 and β = 0.302, respectively; both P < 0.05), and in turn, cortical thickness was associated with higher intelligence (β = 0.198, P < 0.05). Muscular fitness was not related to overall cortical thickness. None of the three physical fitness components were related to surface area (p > 0.05). The associations of cardiorespiratory fitness and speed-agility with overall cortical thickness were mediated by fat mass index (56.86% & 62.28%, respectively). In conclusion, cardiorespiratory fitness and speed-agility, but not muscular fitness, are associated with overall cortical thickness, and in turn, thicker brain cortex is associated with higher intelligence in overweight/obese children. Yet, none of the three physical fitness components were related to surface area. Importantly, adiposity may hinder the benefits of cardiorespiratory fitness and speed-agility on cortical thickness. Understanding individual differences in brain morphology may have important implications for educators and policy makers who aim to determine policies and interventions to maximize academic learning and occupational success later in life., (Copyright © 2018 Elsevier Inc. All rights reserved.)