Interindividual differences in motor network connectivity and behavioral response to iTBS in stroke patients

Area of Science:

• Neuroscience
• Rehabilitation Medicine

Background:

• Repetitive transcranial magnetic stimulation (rTMS) aims to induce cerebral plasticity for neural reorganization, particularly after stroke.
• Interindividual variability in motor improvement following rTMS of the primary motor cortex (M1) is a significant challenge in stroke rehabilitation.

Purpose of the Study:

• To investigate the relationship between interindividual differences in motor network connectivity and behavioral responses to excitatory rTMS in stroke patients.
• To determine if baseline network connectivity predicts the efficacy of intermittent theta-burst stimulation (iTBS) in improving hand motor function after stroke.

Main Methods:

• Functional magnetic resonance imaging (fMRI) and dynamic causal modeling (DCM) were used to assess effective connectivity in motor networks of chronic stroke patients and healthy controls.
• Patients received intermittent theta-burst stimulation (iTBS) over the ipsilesional primary motor cortex (M1) or control stimulation, with motor performance and cortical excitability measured before and after.

Main Results:

• Stronger endogenous coupling between the supplemental motor area (SMA) and M1 was associated with better baseline motor performance in patients.
• iTBS over ipsilesional M1 increased M1 excitability and decreased contralesional M1 excitability compared to control stimulation.
• Individual improvements in hand motor function after iTBS correlated with pre-intervention neural coupling strengths within the stimulated hemisphere, particularly connections to M1.

Conclusions:

• Interindividual variability in response to iTBS for stroke-related motor deficits is influenced by baseline motor network connectivity.
• Baseline connectivity patterns, especially within the lesioned hemisphere's motor network, can predict the effectiveness of rTMS interventions.
• Understanding these connectivity-behavior relationships may help personalize rTMS therapy for stroke patients.