Cortical activation changes underlying stimulation-induced behavioural gains in chronic stroke

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Medical Devices

Background:

• Stroke rehabilitation often seeks adjunct therapies to improve functional recovery.
• Non-invasive brain stimulation, like transcranial direct current stimulation (tDCS), shows potential but its mechanisms post-stroke are unclear.
• Previous studies suggest tDCS may enhance motor cortical activity, but direct evidence linking this to behavioral improvements in stroke patients is lacking.

Purpose of the Study:

• To investigate the direct relationship between ipsilesional cortical activation changes induced by tDCS and behavioral improvements in chronic stroke patients.
• To determine if anodal tDCS to the ipsilesional motor cortex is associated with enhanced motor performance.
• To compare the effects of anodal ipsilesional, cathodal contralesional, and sham tDCS on motor function and brain activity.

Main Methods:

• A study involving chronic stroke patients (at least 6 months post-stroke) with two experiments: behavioral (n=13) and functional magnetic resonance imaging (fMRI) (n=11).
• Three stimulation conditions were tested in separate sessions: anodal tDCS to the ipsilesional hemisphere, cathodal tDCS to the contralesional hemisphere, and sham stimulation.
• Behavioral outcomes (response times) and fMRI-measured cortical activation were assessed for each condition.

Main Results:

• Anodal tDCS to the ipsilesional hemisphere significantly improved response times (5-10%) in the affected hand.
• This behavioral improvement correlated with increased movement-related cortical activity in the primary motor cortex and connected regions.
• Cathodal tDCS to the contralesional hemisphere showed functional improvement compared to sham, but less pronounced than anodal stimulation.

Conclusions:

• Anodal tDCS applied to the ipsilesional motor cortex is an effective adjunct therapy for stroke rehabilitation, improving motor response times.
• The behavioral benefits of anodal tDCS are directly associated with increased neural activity in the ipsilesional primary motor cortex.
• This study provides the first direct evidence linking tDCS-induced cortical changes to functional gains in stroke patients, regardless of disability level.