Assessing tDCS Placebo Effects on EEG and Cognitive Tasks

Area of Science:

• Neuroscience
• Cognitive Psychology

Background:

• Transcranial direct current stimulation (tDCS) has shown potential in enhancing divergent thinking (DT).
• The placebo effect in tDCS research requires thorough investigation to differentiate true stimulation effects from psychological influences.

Purpose of the Study:

• To examine the placebo effect of tDCS on divergent thinking (DT) performance.
• To compare the electroencephalogram (EEG) responses and creativity scores between placebo and control groups.

Main Methods:

• Participants underwent two DT tasks: Alternative Uses Task (AUT) and Instances Task (IT).
• EEG data was recorded, and an automated algorithm removed speech-induced noise.
• Features extracted from EEG data (power, WPSD, WCPSD) were analyzed using Support Vector Machine (SVM) classifiers.
• A placebo group received sham stimulation during the IT, while a control group received no stimulation.

Main Results:

• A significant difference (p<0.001) was observed between no stimulation and sham stimulation conditions compared to the control group.
• The χ²-test confirmed a statistically significant placebo effect in the sham stimulation condition.
• EEG analysis revealed distinct patterns between stimulated and non-stimulated conditions.

Conclusions:

• The study provides robust evidence for a placebo effect in tDCS research related to cognitive enhancement.
• Psychological factors, such as expectation, play a significant role in the perceived efficacy of tDCS.
• Future research should carefully control for placebo effects when evaluating tDCS interventions for cognitive functions like creativity.