The hemispheric divergence model: A conceptual bilateral network framework for motor recovery after stroke

Stroke recovery has traditionally been conceptualized as a process of ipsilesional restoration. However, accumulating evidence from connectomics, functional neuroimaging, and network neuroscience suggests that motor recovery is better understood as a bilateral, systems-level process involving dynamic interactions between the hemispheres. This paper proposes the Hemispheric Divergence Model (HDM), a theoretical framework describing post-stroke motor recovery as an evolving process of interhemispheric network reweighting rather than unilateral repair alone. Within the HDM, the ipsilesional hemisphere undergoes progressive structural degeneration, diaschisis, metabolic suppression, and network fragmentation, while the contralesional hemisphere simultaneously develops compensatory recruitment, hyperconnectivity, and altered transcallosal inhibitory influence. Motor recovery is therefore proposed to be shaped by the evolving interplay between adaptive compensation and maladaptive interhemispheric imbalance, though the precise weighting of these contributions likely varies with lesion severity and structural reserve. The HDM integrates evidence from resting-state functional MRI, diffusion tensor imaging, graph-theoretical connectomics, transcranial magnetic stimulation, and longitudinal network analyses to demonstrate that functional motor outcome is more closely associated with restoration of interhemispheric connectivity than with lesion characteristics alone. The HDM introduces a temporal framework spanning acute, subacute, and chronic recovery phases, highlights critical windows during which network plasticity remains modifiable, and generates specific testable predictions regarding biomarker development, longitudinal connectomic monitoring, and personalised neuromodulatory rehabilitation strategies.