Transcranial Direct Current Stimulation of the Motor Cortex Biases Action Choice in a Perceptual Decision Task

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Science

Background:

• The primary motor cortex (PMC) is crucial for voluntary action selection and execution.
• Understanding how to modulate motor control is key to advancing rehabilitation and human-computer interfaces.

Purpose of the Study:

• To investigate if transcranial direct current stimulation (tDCS) of the PMC can alter hand choice in a perceptual decision-making task.
• To differentiate the effects of anodal and cathodal tDCS on hand selection.

Main Methods:

• Two experiments involving a perceptual decision-making task where participants classified visual stimuli using either their left or right index finger.
• Primary motor cortex (PMC) stimulation using transcranial direct current stimulation (tDCS) under bilateral, anodal unilateral, and cathodal unilateral conditions.
• Sessions were counterbalanced, with stimulation laterality reversed across sessions to control for order effects.

Main Results:

• Anodal tDCS of the PMC biased participants towards using the contralateral hand.
• Cathodal tDCS of the PMC biased participants towards using the ipsilateral hand.
• Reaction times (RT) for the left hand were modulated, showing faster responses when the bias favored the left hand and slower responses when it opposed it.

Conclusions:

• tDCS of the PMC can effectively modulate motor responses and the choice of hand.
• Findings support both perceptual bias and motor-choice bias accounts for tDCS effects.
• This research opens avenues for non-invasive neuromodulation techniques to influence motor behavior.