Action video games (AVGs) offer a powerful experimental paradigm for investigating how sustained cognitive demands reshape the brain’s structural and functional organization. Long-term AVG players—referred to in this dissertation as gamers—engage in high-stakes, fast-paced environments that require rapid transformation of visuomotor information into action selection and adaptive decision-making under uncertainty. Prior research has identified several cognitive enhancements in gamers, including faster response times and improved visuomotor coordination; however, it has lacked mechanistic insight into how the brain from prolonged engagement while playing AVGs orchestrates neuroplastic refinements that give rise to these advantages. This dissertation presents a multi-faceted investigation of neuroplasticity in gamers, across three complementary studies. First, a targeted network analysis revealed enhanced structural and functional connectivity in the dorsal visual streams of gamers. The functional enhancements, both undirected and directed functional connectivity measures, correlated with faster response times. Second, a structurally constrained framework assessed how anatomical connectivity constrains functional and directed interactions. Gamers exhibited connectivity patterns consistent with a shift from feedback-driven object-in-place, iterative corrections to a more anticipatory, feedforward strategy, facilitating streamlined visuomotor transformation, scene integration, attentional control, and adaptive action selection compared with non-gamers. Third, a novel principal component analysis (PCA) method revealed that gamers exhibited a stronger convergence of top-down cognitive clarity, learned value-to-action transformation, and bottom-up motor readiness, factors that were each associated with improved response times. Across these three studies, findings support a proposed framework underlying the observed neuroplastic refinements: Cognitive Resource Reallocation (CRR). While prior research has discussed resource reallocation, this dissertation is the first to formally define CRR as a dynamic neurophysiological process embedded in physically lawful neural dynamics. It describes how functional and metabolic resources are redistributed in response to cognitive strain to support behaviorally relevant processes more effectively. CRR provides a unifying theoretical lens to explain how long-term gameplay leads to the targeted refinement of neural circuits that enable efficient visuomotor decision-making. More broadly, this work positions action video games as an ecologically valid paradigm for studying adaptive neuroplasticity, with implications for cognitive training, rehabilitation, and performance enhancement.