Timing of transcranial direct current stimulation at M1 does not affect motor sequence learning.

Area of Science:

• Neuroscience
• Motor Learning
• Cognitive Enhancement

Background:

• Anodal transcranial direct current stimulation (tDCS) applied to the primary motor cortex (M1) has been investigated for its potential to enhance motor skill acquisition.
• Previous studies suggest that tDCS administered concurrently with motor training may yield the most significant offline performance gains, but these findings often stem from varied experimental methodologies.

Purpose of the Study:

• To investigate the efficacy of a single bout of anodal tDCS applied to M1 at different time points relative to motor training on serial reaction time task (SRTT) performance.
• To determine if tDCS administered before, during, or after SRTT practice influences subsequent skill development and offline learning compared to a no-stimulation control.

Main Methods:

• Ninety participants were randomly assigned to receive 15 minutes of 2 mA anodal tDCS (anode over right M1, cathode over left M1) either before, during, or after practicing an eight-element SRTT, or to a no-tDCS control group.
• Participants used their left hand to perform the SRTT.
• Performance was assessed at 1-hour and 24-hour post-practice test blocks.

Main Results:

• All groups, including the control, demonstrated significant offline gains in SRTT performance at both the 1-hour and 24-hour test intervals.
• There were no statistically significant differences in the trajectory of skill development between the tDCS conditions (before, during, or after practice) and the no-stimulation control group.

Conclusions:

• A single session of anodal tDCS applied to M1 does not appear to significantly enhance motor skill learning or offline gains for a novel SRTT, regardless of its timing relative to practice.
• These findings contribute to a growing body of evidence that questions the effectiveness of single-bout exogenous stimulation protocols as an adjunct to motor training for improving skill acquisition.