Modulating cortical connectivity in stroke patients by rTMS assessed with fMRI and dynamic causal modeling

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Neurology

Background:

• Stroke often impairs motor function due to disrupted interhemispheric motor cortex communication.
• Transcranial magnetic stimulation (TMS) studies suggest abnormal transcallosal inhibition contributes to motor deficits.

Purpose of the Study:

• To investigate if repetitive TMS (rTMS) can modulate pathological cortical motor interactions in subacute stroke patients.
• To assess the impact of rTMS on motor performance and effective neural connectivity using fMRI and DCM.

Main Methods:

• Eleven subacute stroke patients underwent functional magnetic resonance imaging (fMRI) during hand movements.
• Inhibitory 1-Hz rTMS was applied over the vertex (control) and the unaffected primary motor cortex (M1).
• Dynamic causal modeling (DCM) analyzed changes in effective connectivity within a motor network (M1, premotor cortex, SMA).

Main Results:

• rTMS over the unaffected M1 significantly improved paretic hand motor performance.
• Behavioral improvements correlated with reduced inhibitory influences from the unaffected M1.
• rTMS over the unaffected M1 enhanced connectivity between the ipsilesional supplementary motor area (SMA) and M1.

Conclusions:

• rTMS applied to the unaffected M1 can transiently remodel the motor system's functional network architecture.
• Improved motor performance is linked to decreased pathological transcallosal influences and restored ipsilesional SMA-M1 connectivity.