The Frontopolar Cortex and Decision-Making: Null Effects of Intermittent (Two-Block) Cathodal TDCS

Abstract

The frontopolar cortex (FPC) has been implicated in high-level cognitive control, including model-based reasoning, cognitive branching, and the regulation of exploration–exploitation tradeoffs (Koechlin, 2020). While neuroimaging studies have provided strong correlational evidence, causal findings remain limited. In the present study, we tested whether suppression of right FPC activity impairs decision-making performance. Twenty healthy young adults received cathodal transcranial direct current stimulation (tDCS) over the right FPC and sham stimulation on different sessions, using a bipolar montage with two 10-minute blocks of cathodal tDCS separated by a 3-minute pause. Participants then performed a decisionmaking task adapted from the cascade model framework. Performance was analyzed across accuracy, error rates, and missed responses. No significant differences were observed between active and sham groups on any measure, even after excluding participants with atypical learning curves. These null results replicate our prior findings with high-definition tDCS (Timokhov et al., 2025) and add to growing evidence that single-session tDCS produces inconsistent or negligible effects on higher cognition. While our findings do not question the causal role of the FPC in decision-making, they underscore the need for larger samples, online or multi-session protocols, individual electric field modelling, and paradigms that more selectively probe FPC-dependent processes.