Structure-function coupling reveals hemisphere-specific network reorganization after stroke

MRI images are a valuable tool for tracking functional and structural network changes following brain trauma, potentially identifying biomarkers for targeted treatment and innovative neuromodulatory therapies. In the context of ischemic stroke, alterations in functional networks, specifically the contralesional hemisphere, and structural continuity, particularly the corticospinal tract, have been linked to clinical impairment and prognosis.

However, these aspects are frequently examined independently and at individual time intervals, failing to capture the intricate, dynamic nature of brain network plasticity. This study explored structural and functional connectivity (SC-FC) interactions in healthy mice and their evolution following cortical and cortico-striatal injury over a four-week period.

In the normal brain, intra-hemispheric SC-FC coupling was primarily lateralized in the sensorimotor network (SMN), while the default mode network (DMN) showed no discernible hemispheric differences. Within the SMN, intra-hemispheric interactions dominated over inter-hemispheric interactions. After cortical injury, regions exhibiting high initial intra-hemispheric SC-FC coupling maintained their connections, whereas sensorimotor regions with initially weak coupling demonstrated delayed increases in the injured hemisphere.

Intra-hemispheric coupling remained relatively stable in contralesional regions, yet directional inter-hemispheric assessments unveiled targeted adjustments, such as heightened contralesional-to-ischemic coupling in the primary motor cortex and diminished bidirectional coupling in medial sensorimotor cortex. Cortico-striatal stroke resulted in fewer long-term modifications, primarily characterized by diminished inter-hemispheric coupling in the motor cortex.

Notably, these modifications were not solely linked to the extent of lesioned tissue. The findings demonstrate that hemisphere-specific and directional SC-FC coupling can reveal distinct network and injury-model-specific reconfigurations that would otherwise remain undetected when analyzing structural and functional connectivity in isolation.