Cortical Stimulation Paired With Volitional Unimanual Movement Affects Interhemispheric Communication

Area of Science:

• Neuroscience
• Motor Control
• Rehabilitation

Background:

• Cortical stimulation (CS) impacts motor cortex excitability, suggesting rehabilitation potential.
• Existing studies often examine CS during rest or single-hemisphere movement, limiting understanding of interhemispheric interactions during dynamic tasks.

Purpose of the Study:

• To investigate the effects of single-hemisphere CS on motor cortex excitability and interhemispheric interactions during contralateral and ipsilateral limb movements.
• To correlate changes in brain activity with behavioral outcomes (reaction time).

Main Methods:

• CS was applied to one motor cortex in macaques performing a unimanual reaction time task.
• Local field potential (LFP) recordings assessed brain activity and interhemispheric coherence.
• Stimulation timing relative to movement onset and offset was systematically varied.

Main Results:

• Stimulation before contralateral movement onset shortened reaction time.
• Stimulation after contralateral movement onset increased contralateral reaction time but decreased ipsilateral reaction time.
• Stimulation before ipsilateral movement onset decreased ipsilateral reaction time.
• Changes in interhemispheric alpha band coherence correlated with reaction time changes, suggesting a role in interhemispheric communication.

Conclusions:

• The impact of CS on motor cortex functional coupling depends critically on the timing of stimulation relative to limb movement.
• Alpha band activity may serve as an indicator of interhemispheric communication during motor tasks.
• Findings offer insights into optimizing CS protocols for motor rehabilitation.