Altered functional connectivity between cortical premotor areas and the spinal cord in chronic stroke

Background Neuroscience research has contributed significantly to understanding alterations in brain structure and function after ischemic stroke. Technical limitations have excluded the spinal cord from imaging-based research. Available data are restricted to a few microstructural analyses, and functional connectivity data are absent. The present study attempted to close this knowledge gap and assess alterations in corticospinal activation and coupling changes in chronic stroke. Methods Thirteen well-recovered stroke patients underwent corticospinal functional MRI while performing a simple force generation task. Task-related activation was localized in the ipsilesional primary motor cortex (M1), ventral premotor cortex (PMV), and supplementary motor area (SMA), as well as in the cervical spinal cord. Psycho-physiological interactions and linear modeling were used to infer functional connectivity between cortical motor regions and the cervical spinal cord and their associations with motor deficits. Results The main finding was that PMV and SMA showed topographically distinct alterations in their connectivity with the spinal cord. Specifically, we found a reduced coupling between SMA and the ipsilateral ventral spinal cord and an enhanced coupling between PMV and ventral and intermediate central spinal zones. Lower SMA- and higher PMV-related spinal cord couplings were correlated with residual deficits. Conclusion This work provides first-in-human functional insights into stroke-related alterations in the functional connectivity between cortical motor areas and the spinal cord, suggesting that different premotor areas and spinal neuronal assemblies might be involved in coupling changes. It adds a novel, promising approach to better understanding stroke recovery and developing innovative models to comprehend treatment strategies with spinal cord stimulation.