High-Definition tDCS of the DLPFC: Effects on Effort-Related Cardiac Reactivity Across Sexes

This study was designed to examine the effect of frontal hemispheric asymmetry (FHA) on effort-related cardiovascular responses. High-definition transcranial direct current stimulation (HD-tDCS) was applied to the dorsolateral prefrontal cortex (dlPFC) to manipulate FHA and investigate its impact on cardiovascular reactivity. The sample consisted of 45 female and 44 male participants, who received either left or right cathodal stimulation. Following stimulation, participants performed two types of task demands: one fixed and easy, the other unfixed. In both tasks, participants could earn a moderate monetary reward. We measured pre-ejection period (PEP), heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP). Drawing on motivation intensity theory (MIT), we predicted that right cathodal stimulation (left FHA) would lead to higher perceived success importance to get the reward determining higher effort in the unfixed task demand compared to the left cathodal stimulation and both stimulation conditions in the fixed task. As predicted, PEP reactivity was stronger in the unfixed condition following right cathodal stimulation compared to left cathodal stimulation and both stimulation conditions in the fixed task. Importantly, this effect was observed across both female and male participants, extending earlier neuromodulation findings (previously shown only in female samples) to both sexes. Overall, the results indicate that dlPFC neuromodulation can lead to higher effort by shifting frontal asymmetry and enhancing the perceived success importance in reward-driven tasks.