No effect of preliminarily simulated cathodal HD-tDCS on the frontopolar cortex in the exploration-exploitation task.

This study investigated the causal role of the human frontopolar cortex (FPC) in managing counterfactual strategies during decision-making under uncertainty. Using a combination of cathodal high-definition transcranial direct current stimulation (HD-tDCS) and computational modeling, we examined how cathodal stimulation, preliminarily simulated with SimNIBS, affects the retrieval of alternative strategies in the task that constantly provokes exploration-exploitation dilemmas. A comparison of resting-state recordings with functional near-infrared spectroscopy (fNIRS) before and after stimulation did not reveal any physiological effect of HD-tDCS. Furthermore, there was no significant difference in participants' exploratory behavior between the sham and cathodal groups. These results indicate that the employed HD-tDCS protocol may not sufficiently influence FPC function, despite preliminary tDCS simulations with SimNIBS, calling for further refinement of the HD-tDCS protocol used in future research to elucidate the causal role of the FPC in decision-making under uncertainty.