Measure Striatal Adenosine-Dopamine Receptor Interactions from Molecules to Behaviors Using Caffeine and PET/MRI in Healthy Adults

What this Trial Is About

Researchers are investigating how caffeine intake influences the learning process through reward feedback compared to a placebo. This study focuses on healthy adults aged 18 to 45 and aims to better understand the role of caffeine in dopamine-related reinforcement learning. The research explores interactions between adenosine 2A receptors and dopamine D2 receptors in the brain, which are important for learning and behavior, using advanced brain imaging techniques. Participants will take part in a double-blind randomized crossover study where they receive either a 200mg caffeine tablet or a placebo lactose tablet. Before each study day, participants undergo a 6-day period without caffeine, alcohol, or drugs and maintain regular sleep schedules. On the seventh day, they undergo simultaneous PET/fMRI brain scans after taking the assigned tablet 20 minutes prior to scanning. These scans will measure dopamine receptor availability and brain activity during reinforcement learning and motor inhibition tasks. During the study visits, participants complete a Probabilistic Selection Task (reinforcement learning) and a Go/NoGo task (motor inhibition) while being scanned. Researchers monitor dopamine D2/D3 receptor availability with PET using a radioactive dye and brain activity with fMRI. The study also assesses salience attribution after scanning. Safety is monitored, and participants' adherence to the washout period is required. The main outcomes include dopamine receptor availability and effects of caffeine on learning tasks during the scan. The total participation includes the washout and scan days, with follow-up assessments after the scan.

Effects of Caffeine on Reinforcement Learning in Healthy Adults Using PET/MRI