Cathodal tDCS increases stop-signal reaction time.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neuromodulation

Background:

• Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique.
• The effects of tDCS on cognitive tasks are often assumed to be polarity-dependent, with anodal stimulation enhancing and cathodal stimulation impairing performance.
• Cathodal tDCS effects, particularly on response inhibition, remain underexplored.

Purpose of the Study:

• To investigate the effects of cathodal tDCS on response inhibition.
• To examine if cathodal tDCS over the right dorsolateral prefrontal cortex (rDLPFC) impairs performance on the stop-signal task (SST).

Main Methods:

• Forty-five healthy adults received either cathodal tDCS or sham stimulation over the rDLPFC.
• The stop-signal task (SST) was used to measure response inhibition, with stop-signal reaction time (SSRT) as the primary outcome.
• A 9 cm² cathode was placed over the rDLPFC, and a 35 cm² anode was placed over the left deltoid.

Main Results:

• A significant Time × tDCS condition interaction was observed.
• Cathodal tDCS over the rDLPFC led to a significant increase in SSRT, indicating impaired response inhibition.
• These findings contrast with previous research showing enhanced SST performance with anodal tDCS over the same region.

Conclusions:

• Cathodal tDCS over the rDLPFC can impair response inhibition.
• Response inhibition is sensitive to the neural state of the rDLPFC, modulated by tDCS polarity.
• The findings highlight the differential effects of tDCS polarity on cognitive functions.