# The effect of transcranial direct current stimulation on frontal alpha asymmetry and visuospatial attention in food-reward contexts: a triple-blind randomized sham-controlled study

## TL;DR

This study investigated how transcranial direct current stimulation affects brain activity and attention in food-related contexts, finding no behavioral changes but some neural effects.

## Contribution

The study provides new insights into the neural mechanisms of attentional bias in reward contexts using tDCS and FAA.

## Key findings

- tDCS did not affect frontal alpha asymmetry or behavioral attentional bias and disengagement.
- Exploratory analyses showed tDCS-induced attentional bias for rewards in neural responses.
- No behavioral changes were observed despite neural effects, suggesting a dissociation between neural and behavioral outcomes.

## Abstract

Research indicates a connection between right frontal brain activity dominance and the inhibitory system. However, the underlying brain mechanism regarding attentional control remains unclear. In this preregistered experiment, we explored the association between frontal alpha asymmetry (FAA) — which is an electrophysiological measure of the difference in alpha power between the left and right dorsolateral prefrontal cortex — and the behavioral and brain activity components of attentional bias and disengagement, as observed in a visuospatial cueing (VSC) task.

We used a triple-blind randomized sham-controlled design with 65 (Mage = 23.93; SDage = 6.08; 46 female) healthy humans. Participants’ resting-state EEG was recorded to calculate FAA scores before and after 2 mA anodal transcranial direct current stimulation (tDCS) to the right frontal site for 20 min. They also completed a VSC task with neutral and intrinsic reward-associated (food) conditions.

Results indicated no impact of tDCS on FAA or behavioral attentional bias and disengagement. Exploratory analyses revealed tDCS-induced attentional bias for rewards, as detected in enhanced Late Directing Attention Positivity and P1 effect. However, these effects did not translate into observable behavioral changes.

The enhanced attentional bias may result from tDCS-induced enhancement of top-down attentional orienting to spatial locations associated with reward-related stimuli, potentially mediated by noradrenergic mechanisms.

The online version contains supplementary material available at 10.1186/s40359-025-02972-x.