Transcranial direct current stimulation above the medial prefrontal cortex facilitates decision-making following periods of low outcome controllability

Abstract

Recent studies suggest that choice behavior in reinforcement learning tasks is shaped by the level of outcome controllability. In particular, “Pavlovian bias” (PB) seems to be enhanced under low levels of control, manifesting in approach tendencies towards rewards and response inhibition when facing potential losses. The medial prefrontal cortex (mPFC) has been implicated both in evaluating outcome controllability and in the recruitment of cognitive control to suppress maladaptive PB during reinforcement learning. The current study tested if high-definition transcranial direct current stimulation (HD-tDCS) above the mPFC of healthy humans can influence PB, and counteract the previously documented, deleterious behavioral effects of low outcome controllability on decision-making. In a pre-registered, between-group, double-blind study (N = 103 adults, both sexes), we tested the interaction between controllability and HD-tDCS on parameters of choice behavior in a Go/NoGo task. Relative to sham stimulation, HD-tDCS resulted in more robust performance improvement following reduced control, an effect that was more pronounced in appetitive trials. In addition, we found evidence for weaker PB when HD-tDCS was administered during low controllability over outcomes. Computational modeling revealed that parameter estimates of learning rate and choice randomness were modulated by controllability, HD-tDCS and their interaction. Overall, these results highlight the potential of our HD-tDCS protocol for interfering with choice arbitration under low levels of control, resulting in more adaptive behavior.

Significance statement

Our decisions are shaped by how much control we have over the situation. Under extreme circumstances, low controllability of choice outcomes can lead to learned helplessness (LH) and impaired coping. Since the medial prefrontal cortex was implicated in LH, we tested if high-definition transcranial direct current stimulation (HD-tDCS) of this region counteracts the deleterious effects of low controllability of rewards and losses in healthy humans. We found stronger improvement in response accuracy when low controllability was combined with HD-tDCS. Moreover, several latent parameters of choice behavior were influenced by HD-tDCS and/or controllability. These results highlight the potential of our HD-tDCS protocol for interfering with choice arbitration in environments with reduced controllability, resulting in more adaptive behavior.