Abstract
The ability to manipulate dopamine in vivo through non-invasive, reversible mechanisms has the potential to impact clinical, translational, and basic research. A recent PET study demonstrated that a single session of prefrontal transcranial direct current stimulation (tDCS) increased striatal dopamine binding. We sought to extend this work by examining whether prefrontal tDCS could increase both dopamine levels and behavior. We conducted a between-subjects study (n=30) using active and sham tDCS and used spontaneous eye blink rate as an indirect proxy for dopamine functioning. The initial design and analyses were pre-registered (https://osf.io/gmnpc). While stimulation did not show an effect for any of the basic pre-registered analyses, we identified individual differences suggesting that baseline dopamine has an effect on tDCS stimulation. Baseline dopamine was positively related to change in dopamine within the active stimulation group but negatively related to change within the sham stimulation group. While this pre-registered design involved a small sample size, it provides critical information about how studies of tDCS need to account for baseline dopamine levels when interpreting tDCS stimulation response.