Brain Lateralization Enhanced by Long-Term Intensive Training and its Resilience to Short-Term Concussion in Elite Athletes

Background: Brain lateralization, the hemispheric specialization of functional networks, is essential for motor and cognitive functions. However, how intensive athletic training shapes hemispheric organization remains poorly understood. This study investigated the formation of functional lateralization in elite athletes through long-term intensive training and its potential alteration due to external factors, specifically sport-related concussions. Methods: Resting-state fMRI data were collected from 13 world class gymnasts (WCGs) and 14 non-athletic controls. Longitudinal data were collected from 18 soccer players and 8 golfers before and after one season, with concussions monitored in the soccer players. Hemispheric integration and segregation laterality indices (LI int and LI seg ) were calculated to quantify hemispheric differences in information processing for each brain region, and the standard laterality index (LI) was employed to measure hemispheric asymmetry. Associations between laterality indices and neurotransmitter receptor/transporter densities were examined. Post-season changes in these indices were assessed to evaluate concussion effects on brain lateralization. Results: The WCGs showed significantly increased LI int in several left-hemispheric regions, including the precentral gyrus, cingulate gyrus, thalamus, superior parietal lobule, and lateral occipital cortex compared with the HCs, though no results were found in LI seg . Furthermore, the LI analysis revealed that the WCGs demonstrated higher hemispheric asymmetry in the left precentral gyrus, cingulate gyrus, and thalamus. These laterality indices also showed positive correlations with certain neurotransmitters. Similar patterns of enhanced lateralization and neurotransmitter associations were observed in soccer players and golfers. However, no significant changes in laterality indices were observed as a result of concussions sustained during the season. Conclusions: Long-term intensive training enhances functional integration in the left hemisphere, leading to stable brain lateralization patterns resilient to sport-related concussions.