Inhibitory and excitatory motor cortex dysfunction persists in the chronic poststroke recovery phase

Area of Science:

• Neuroscience
• Motor Control
• Rehabilitation Science

Background:

• Stroke frequently impairs motor function due to damage in the motor cortex.
• Understanding neurophysiological changes in the motor cortex is crucial for stroke recovery.
• Transcranial magnetic stimulation (TMS) allows assessment of cortical excitability.

Purpose of the Study:

• To compare intracortical facilitation (ICF) and intracortical inhibition (ICI) between chronic stroke survivors and healthy individuals.
• To investigate motor cortex excitability differences using TMS.

Main Methods:

• Single- and paired-pulse TMS applied to the motor cortex of 14 stroke survivors and 19 healthy controls.
• Motor evoked potentials recorded from the first dorsal interosseus muscle.
• Comparison of motor threshold, ICF, ICI, and ICF/ICI ratio between groups.

Main Results:

• Stroke survivors had higher motor thresholds and lower ICI compared to controls.
• The ICF/ICI ratio was significantly lower in stroke survivors, indicating impaired cortical inhibition.
• Reduced motor cortex excitability was observed in chronic stroke survivors.

Conclusions:

• Stroke survivors exhibit reduced motor cortex excitability, characterized by impaired intracortical inhibition and facilitation.
• These findings highlight neurophysiological deficits in the chronic poststroke phase.
• Interventions aimed at normalizing motor cortex excitability may enhance motor recovery prospects.