Stimulation of the human ventral tegmental area increases strategic betting

Learning is a fundamental aspect of human behaviour and is essential for adapting to new environments and situations. The ventral tegmental area is a critical brain area containing neurons that release dopamine to signal reward, drive learning and bias decision-making. Human data on the ventral tegmental area's effects on cognition are scarce, and no studies have causally manipulated the human ventral tegmental area. Here we studied a unique group of patients who had deep brain stimulation surgery in the ventral tegmental area to improve pain due to trigeminal autonomic cephalalgias refractory to medical therapy. In this study, we asked how deep brain stimulation, which aimed to inhibit the ventral tegmental area, affected reward-related learning and decision-making. Patients performed a reversal learning task while their deep brain stimulation was switched on versus off, in a powerful within-subject design. In the task, patients learned to choose between two options to win money, based on previous outcomes, but also made post-decision bets based on whether they thought they were likely to win. This allowed us also to investigate the effect of electrical stimulation within the ventral tegmental area on betting behaviour. We found that stimulation did not affect learning in this group of patients but led to a more strategic betting behaviour. First, stimulation reduced the bias whereby healthy people tend to bet similarly to the previous trial. Second, when on stimulation, bets were more strongly linked to the actual value of the choice. The data indicate that disrupting ventral tegmental area signals by electrical stimulation reduces the perseverative betting bias, permitting more strategic decision-making. We interpret this to mean that mesolimbic dopaminergic signals in humans may be important in producing persistence of reward-driven behaviours over time.