Neuromodulation of risk and reward processing during decision making in individuals with general anxiety disorder (GAD)

Individuals with general anxiety disorder (GAD) have an impaired future-oriented processing and altered reward perception, which might involve the ventromedial prefrontal cortex (vmPFC) and dorsolateral prefrontal cortex (dlPFC). Twenty-nine adults with GAD performed the balloon analogue risk-taking task (BART) and delay discounting task (DDT) during five sessions of transcranial direct current stimulation (tDCS) with different stimulation conditions. The stimulation conditions were: anodal dlPFC (F3)/cathodal vmPFC (Fp2), anodal vmPFC (Fp2)/cathodal dlPFC (F3), anodal dlPFC (F3)/cathodal right shoulder, anodal vmPFC (Fp2)/cathodal left shoulder, and sham stimulation. Cognitive modeling was used to extract process-based measures. The process-based modeling measures, rather than conventional outcome-based measures, showed a significant effect of stimulation condition. All real stimulation conditions improved the updating rate of prevalence, and risk taking in the BART. Moreover, for anodal dlPFC (F3)/cathodal vmPFC (Fp2), anodal vmPFC (Fp2)/cathodal dlPFC (F3), and anodal vmPFC (Fp2)/cathodal left shoulder stimulations we have observed an improvement in prior beliefs about the explosion. Also, for anodal dlPFC (F3)/cathodal vmPFC (Fp2), anodal dlPFC (F3)/cathodal right shoulder, anodal vmPFC (Fp2)/cathodal left shoulder we have observed more stable choice pattern. the DDT, exponential discounting rate and randomness were improved during anodal dlPFC and anodal vmPFC stimulation with extracranial return electrodes. Different roles of the targeted areas are discussed based on significant performance differences resulting from the specific electrode positions. The results suggest that different domains of reward processing are controlled by the vmPFC and dlPFC. The vmPFC is more relevant for value-based decision making with a positive expectation and chance-based randomness, whereas the dlPFC is more relevant for logic-based decision making.