Propranolol Reduces Parkinson's Tremor and Inhibits Tremor-Related Activity in the Motor Cortex: A Placebo-Controlled Crossover Trial.

Objective: Parkinson's disease (PD) resting tremor is thought to be initiated in the basal ganglia and amplified in the cerebello-thalamo-cortical circuit. Because stress worsens tremor, the noradrenergic system may play a role in amplifying tremor. We tested if and how propranolol, a non-selective beta-adrenergic receptor antagonist, reduces PD tremor and whether or not this effect is specific to stressful conditions.

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.

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.