Transcranial direct current stimulation improves ipsilateral selective muscle activation in a frequency dependent...

Area of Science:

• Neuroscience
• Motor Control
• Rehabilitation

Background:

• Impaired antagonist muscle suppression causes movement dysfunction, like abnormal muscle synergies post-stroke.
• The selectivity ratio (SR) measures upper limb synergy, assessed via biceps brachii (BB) motor evoked potentials.
• Cathodal transcranial direct current stimulation (c-TDCS) over the primary motor cortex (M1) unexpectedly improves SR in healthy adults and stroke patients.

Purpose of the Study:

• Investigate if selective muscle activation (biceps brachii) depends on movement frequency.
• Determine if c-TDCS-mediated SR improvement is frequency-dependent.
• Explore c-TDCS efficacy for enhancing motor control at challenging movement rates.

Main Methods:

• Seventeen healthy participants performed repetitive isometric elbow flexion and forearm pronation at three frequencies.
• c-TDCS or sham stimulation was applied to the left primary motor cortex (M1) before and after tasks.
• The selectivity ratio (SR) was calculated using biceps brachii (BB) motor evoked potentials.

Main Results:

• Ipsilateral c-TDCS significantly improved the SR in a frequency-dependent manner.
• c-TDCS achieved this by selectively suppressing biceps brachii (BB) antagonist muscle excitability.
• The improvement in SR was more pronounced at higher movement frequencies.

Conclusions:

• c-TDCS is an effective tool for enhancing selective muscle activation.
• c-TDCS efficacy in improving SR is dependent on task frequency.
• Findings suggest c-TDCS benefits task performance at movement rates where selective activation is crucial.