An Integrative Clustering Approach to tDCS Individual Response Variability in Cognitive Performance: Beyond a Null...

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neuromodulation

Background:

• Transcranial direct current stimulation (tDCS) is increasingly studied for cognitive enhancement.
• Existing research on tDCS for working memory shows inconsistent results.
• Inter-individual variability in response to tDCS is a potential confounding factor.

Purpose of the Study:

• To investigate the effects of anodal tDCS on working memory performance.
• To examine the role of inter-individual variability in tDCS response.
• To identify subgroups of responders using an integrative clustering approach.

Main Methods:

• An intra-individual, cross-over, sham-controlled design was employed.
• Healthy volunteers received offline anodal tDCS (1.5 mA, 15 min) to the left prefrontal cortex (LPFC).
• Working memory was assessed using n-back and Sternberg tasks pre- and post-stimulation.
• Cluster analysis was used to differentiate individual responses.

Main Results:

• Overall, anodal tDCS did not significantly improve working memory performance in the total sample.
• Cluster analysis identified a subgroup of 'responders' exhibiting performance improvements after anodal tDCS compared to sham.
• The proportion of responders varied significantly (15%-59%) across different task metrics.

Conclusions:

• High inter-individual variability exists in the response to LPFC tDCS for working memory.
• tDCS may not be a universally effective tool for enhancing working memory in healthy individuals.
• Clustering methods are valuable for identifying responders and assessing tDCS efficacy.