TDCS over PPC or DLPFC does not improve visual working memory capacity.

Area of Science:

• Cognitive Neuroscience
• Neurostimulation

Background:

• Non-invasive brain stimulation, like transcranial direct current stimulation (tDCS), is explored for cognitive enhancement.
• Previous studies on tDCS and visual working memory (VWM) show inconsistent results, potentially due to methodological limitations.

Purpose of the Study:

• To conceptually replicate a high-profile study on anodal tDCS over the posterior parietal cortex (PPC) and dorsolateral prefrontal cortex (DLPFC) for VWM capacity and precision.
• To address methodological issues and increase statistical power compared to the original study.

Main Methods:

• A pre-registered conceptual replication study with 48 participants.
• Participants received counterbalanced anodal tDCS over PPC, DLPFC, or sham stimulation.
• A continuous orientation-reproduction task was used to assess VWM capacity and precision across different loads.

Main Results:

• No evidence was found for a selective improvement in VWM capacity or precision following PPC stimulation.
• tDCS effects on VWM were absent regardless of stimulation site (PPC or DLPFC) or VWM load.
• Bayesian evidence substantially supported the absence of tDCS effects.

Conclusions:

• Single-session anodal tDCS over the PPC does not appear to enhance VWM capacity or precision.
• The findings challenge previous reports of cognitive benefits from PPC-tDCS on VWM.
• Methodological rigor and adequate sample sizes are crucial for reliable neurostimulation research.