A Cortico-Muscular-Cortical Functional Coupling Network for Evaluating Short-Term Effect of rTMS in Stroke Patients

Objective: Repetitive transcranial magnetic stimulation (rTMS) has been applied as an intervention approach for stroke patients during rehabilitation therapy. However, the mechanisms underlying the effects of rTMS on rehabilitation remain unclear. This study aimed to analyze the differences before and after single-trial rTMS to investigate the underlying mechanisms. Methods: In this study, we constructed a cortico-muscular-cortical functional coupling network (CMCFCN) using partial directed coherence (PDC) and performed a quantitative analysis of the network differences before and after rTMS using the symmetry index (SymI) and graph theory metrics. Results: In the stimulation group, the corticomuscular coupling strength of the unaffected side reduced throughout the motor task after rTMS. Comparison analysis of the SymI demonstrated that after rTMS, the stimulation group (before rTMS: 0.8485 ± 0.0499; after rTMS: 0.8893 ± 0.0486) had a tendency towards the balance in corticomuscular coupling strength between the two hemispheres, while the sham stimulation group (before rTMS: 0.8596 ± 0.0305; after rTMS: 0.8788 ± 0.0328) has no significant change. Furthermore, we discovered that the directed local efficiency and directed clustering coefficient of the sensorimotor areas increase significantly in the stimulation group after rTMS in comparison to before rTMS, while no significant increased were seen in the sham stimulation group. Conclusion: Low-frequency rTMS applied to stroke patients can inhibit compensatory movements on the unaffected side, promoting a functional balance between the two hemispheres of the brain. This allowed us to gain insight into the possible applications of rTMS in rehabilitation therapy.