Physical fitness and brain source localization during a working memory task in children with overweight/obesity: The ActiveBrains project

The present study aims (i) to examine the association of physical fitness components (i.e., cardiorespiratory fitness, speed-agility, and muscular fitness) with brain current source density during working memory; and (ii) to examine whether fitness-related current density was associated to working memory performance and academic achievement. Eighty-five children with overweight/obesity aged 8-11 years participated in this cross-sectional study. Physical fitness components were assessed using the ALPHA test battery. Electroencephalography recordings were performed during a Delayed Non-Match-to-Sample task that assessed working memory. Brain source analysis was carried out using sLORETA to estimate regional current source density differences between high and low (H-L) working memory loads. Academic achievement was measured by the Spanish version of the Woodcock-Johnson III test battery. The main results showed that higher cardiorespiratory fitness was associated with higher H-L current density differences in frontal, limbic and occipital regions during encoding and maintenance task's phases (β≥0.412, P≤0.019). A limbic area was further related to better working memory performance (β=0.267, P=0.005). During retrieval, higher cardiorespiratory fitness was also associated with higher current density in temporal regions (β=0.265, P=0.013), whereas lower muscular fitness was associated with higher current density in frontal regions (β=-0.261, P=0.016). Our results suggest that cardiorespiratory fitness, but not speed-agility nor muscular fitness, is positively associated with brain current source density during working memory processes in children with overweight/obesity. Fitness-related current density differences in limbic regions were associated with better working memory.