Transcranial direct current stimulation over the frontal eye field has no effect on visual search performance

Top-down attention (i.e. the goal-directed (de-)prioritization of information) is fundamental for successful everyday life. Attention deficits caused by brain lesions, like visuospatial neglect or extinction, are therefore of major importance and call for effective therapies. Transcranial direct current stimulation (tDCS), a non-invasive, electric brain stimulation technique, has been discussed as a potential therapeutic tool. Recent research suggests that anodal tDCS over the frontal eye field (FEF) might increase visual search performance even in healthy participants, substantiating the potential therapeutic efficacy of tDCS (e.g. for stroke rehabilitation). In two pre-registered experiments, we investigated the robustness of these findings. In the first experiment, the right FEF was anodally stimulated, supposedly increasing neural activity; in the second experiment, anodal tDCS was delivered over the left FEF, and the size of the visual search field was manipulated. In neither of the two experiments, previous findings of enhanced visual search performance due to tDCS could be reproduced. In contrast, Bayesian statistics indicated evidence against reliable top-down attention-guided visual search improvements through FEF tDCS in healthy participants. Although effects might be stronger in patient populations, the present results do not suggest tDCS over FEF to be a very strong candidate as a therapeutical approach in attention disorders.