Effect of striatal dopamine on Pavlovian bias. A large [¹⁸F]-DOPA PET study.

Interaction between Pavlovian and instrumental control systems is key for adaptive motivated behavior, but also plays an important role in various neuropsychiatric disorders, including depression, addiction, and anxiety. Here, we employed the flouorodopa positron emission tomography ([¹⁸F]-DOPA PET) in healthy participants ( = 100) to assess whether dopamine synthesis capacity (K), specifically in the ventral striatum, accounts for individual variation in Pavlovian-to-instrumental transfer (PIT). Surprisingly, this was not the case.

Striatal dopamine dissociates methylphenidate effects on value-based versus surprise-based reversal learning.

Psychostimulants such as methylphenidate are widely used for their cognitive enhancing effects, but there is large variability in the direction and extent of these effects. We tested the hypothesis that methylphenidate enhances or impairs reward/punishment-based reversal learning depending on baseline striatal dopamine levels and corticostriatal gating of reward/punishment-related representations in stimulus-specific sensory cortex. Young healthy adults (N = 100) were scanned with functional magnetic resonance imaging during a reward/punishment reversal learning task, after intake of methylphenidate or the selective D-receptor antagonist sulpiride.

Effects of average reward rate on vigor as a function of individual variation in striatal dopamine.

Rationale: We constantly need to decide not only which actions to perform, but also how vigorously to perform them. In agreement with an earlier theoretical model, it has been shown that a significant portion of the variance in our action vigor can be explained by the average rate of rewards received for that action. Moreover, this invigorating effect of average reward rate was shown to vary with within-subject changes in dopamine, both in human individuals and experimental rodents.

Striatal dopamine synthesis capacity reflects smartphone social activity.

Striatal dopamine and smartphone behavior have both been linked with behavioral variability. Here, we leverage day-to-day logs of natural, unconstrained smartphone behavior and establish a correlation between a measure of smartphone social activity previously linked with behavioral variability and a measure of striatal dopamine synthesis capacity using [F]-DOPA PET in (N = 22) healthy adult humans. Specifically, we find that a higher proportion of social app interactions correlates with lower dopamine synthesis capacity in the bilateral putamen.

The cognitive effects of a promised bonus do not depend on dopamine synthesis capacity.

Reward motivation is known to enhance cognitive control. However, detrimental effects have also been observed, which have been attributed to overdosing of already high baseline dopamine levels by further dopamine increases elicited by reward cues. Aarts et al.

Methylphenidate boosts choices of mental labor over leisure depending on striatal dopamine synthesis capacity.

The cognitive enhancing effects of methylphenidate are well established, but the mechanisms remain unclear. We recently demonstrated that methylphenidate boosts cognitive motivation by enhancing the weight on the benefits of a cognitive task in a manner that depended on striatal dopamine. Here, we considered the complementary hypothesis that methylphenidate might also act by changing the weight on the opportunity cost of a cognitive task, that is, the cost of foregoing alternative opportunity.