Flexible modularity in the human brain: How network architecture reconfigures over time

Modular organization-densely interconnected subsystems linked by sparser between-module connections-is a defining feature of human brain networks. Yet modularity is not static: it reconfigures over seconds during cognition, adapts cumulatively over learning and training, is reshaped over years across development and ageing, and is disrupted and reorganized under neuropathological conditions. Across these domains, empirical findings can appear inconsistent, in part because similar values of global modularity may arise from qualitatively different underlying network reorganizations, including changes in within-module cohesion, between-module coupling, and community composition across scales. Here we synthesize evidence across cognition, learning, and lifespan research to show that modularity change is best understood as a repertoire of timescale-dependent reconfiguration modes rather than as a single scalar property. We further show that this framework extends to neuropathological conditions, where structural damage and compensatory reorganization alter modular organization within the same repertoire of reconfiguration modes. By organizing reported findings into key modes-such as transient integration, selective decoupling and stabilization, and slow long-term rebalancing-and relating them to established biological mechanisms and constraints, we provide a unifying conceptual framework for interpreting flexible modularity as a core principle of adaptive brain organization.