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

## TL;DR

This study found that simulated cathodal HD-tDCS on the frontopolar cortex did not affect decision-making behavior or brain activity in a task involving exploration and exploitation.

## Contribution

The study demonstrates the limitations of a specific HD-tDCS protocol in influencing FPC function during decision-making tasks.

## Key findings

- Cathodal HD-tDCS did not significantly alter participants' exploratory behavior compared to sham stimulation.
- Resting-state fNIRS recordings showed no physiological changes after HD-tDCS.
- The used HD-tDCS protocol may not effectively modulate FPC function despite preliminary simulations.

## Abstract

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.

The online version contains supplementary material available at 10.1038/s41598-025-22016-z.