Cortical excitability in chronic stroke and modulation by training: a TMS study

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Clinical Neurology

Background:

• Gamma-aminobutyric acid (GABA) is implicated in cortical plasticity regulation following stroke.
• Understanding GABAergic system changes is crucial for stroke recovery strategies.

Purpose of the Study:

• To assess intracortical inhibitory and facilitatory circuits in stroke patients' affected hemispheres over 6 months post-stroke.
• To examine how a single training session modulates cortical excitability in chronic stroke survivors.

Main Methods:

• Transcranial magnetic stimulation (TMS) with paired-pulse stimulation was used to evaluate cortical excitability.
• 22 chronic stroke patients (>6 months) and age/gender-matched healthy controls participated.
• Measurements were taken before and up to 30 minutes after a 15-minute training session of 1 Hz thumb movements.

Main Results:

• Stroke patients exhibited reduced intracortical inhibition in the affected hemisphere compared to controls (P = .004).
• A brief decrease in motor evoked potentials occurred post-training in both groups (patients P = .002, controls P = .06).
• Healthy participants showed decreased inhibitory activity post-training, while stroke patients did not exhibit significant changes.

Conclusions:

• Inhibitory intracortical circuits are less active in the chronic stage after stroke.
• A single training session does not modulate inhibitory activity in chronic stroke patients.
• Intracortical disinhibition might be beneficial for stroke recovery, but the capacity for modulation appears impaired long-term.