Anodal tDCS of dorsolateral prefontal cortex during an Implicit Association Test

Anodal stimulation of dorsolateral prefrontal cortex by transcranial Direct Current Stimulation (tDCS) has been shown to enhance performance on working memory tasks. However, it is not yet known precisely which aspects of working memory - a broad theoretical concept including short-term memory and various executive functions - are involved in such effects. In the current study, we aimed to determine whether tDCS would reduce bias effects on an Implicit Association Test, in which subjects must respond either congruently or incongruently to pre-existing evaluative associations. Such biases reflect a conflict between automatic associations and executive function, and tDCS was hypothesized to cause a shift in this balance in favor of executive function. The results clearly contradicted this hypothesis: tDCS did improve reaction times, but in the congruent rather than incongruent mapping condition. We conclude that DLPFC tDCS does not directly improve the ability to overcome bias; previous findings concerning working memory enhancement appear to reflect effects on a different component of executive function.