Dynamic Interactions Between Hemispheres Reveal a Compensatory Pathway for Motor Recovery in Moderate-to-Severe...

Area of Science:

• Neuroscience
• Neuroimaging
• Rehabilitation Medicine

Background:

• Current noninvasive brain stimulation for post-stroke motor recovery often uses the interhemispheric inhibition model, which is less effective for severely affected patients.
• Mechanisms of recovery in moderate-to-severe stroke are not well understood, limiting targeted treatment development.

Purpose of the Study:

• To investigate neural reorganization and interhemispheric interactions in patients with moderate-to-severe subcortical stroke using novel dynamic analysis methods.
• To identify recovery-related functional connectivity alterations and compensatory pathways.

Main Methods:

• Analysis of resting-state functional magnetic resonance imaging (rs-fMRI) data from patients and healthy controls.
• Development and application of dynamic lag analysis to identify altered interhemispheric interactions in sensorimotor regions.
• Development of dynamic lateralization approaches to detect large-scale functional connectivity (FC) alterations during transient lateralization states.

Main Results:

• Dynamic time-lag analysis showed reduced synchronized states in the homotopic dorsal premotor cortex (PMd) post-intervention, correlating with motor recovery.
• Dynamic lateralization analysis revealed a prolonged segregation state with weakened interhemispheric and strengthened intrahemispheric interactions.
• Patients exhibited decreased ipsilesional PMd FC and increased contralesional PMd FC with subcortical networks in the segregation state; these changes were not detected by static analysis.

Conclusions:

• Dynamic analyses of interhemispheric interactions are crucial for understanding post-stroke neural reorganization.
• Diminished homotopic PMd interactions suggest a compensatory mechanism.
• A state-dependent compensatory pathway was identified where the contralesional PMd takes over functions via enhanced subcortical interactions, offering potential for improved interventions.