Effects of Caffeine on Reinforcement Learning and Brain Dopamine Receptor Interactions Measured by PET/MRI in Healthy Adults

What this Trial Is About

Researchers are investigating how caffeine affects the learning process through reward feedback compared to a placebo in healthy adults aged 18 to 45 who regularly consume caffeine. This Phase 4 study focuses on understanding the interaction between adenosine 2A receptors and dopamine D2/D3 receptors in the brain, which are involved in reinforcement learning, a key cognitive process related to habits, preferences, and resistance to change. The study aims to clarify how caffeine, as an adenosine antagonist, influences these brain receptors and learning behaviors using advanced brain imaging techniques. Participants will be given either a 200 mg caffeine tablet or a placebo tablet 20 minutes before undergoing a brain scan using simultaneous positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). Before each scan day, participants will complete a 6-day washout period abstaining from caffeine, alcohol, and drugs while maintaining regular sleep patterns. During the scan, participants perform a reinforcement learning task and a motor inhibition task to assess brain activity and dopamine receptor availability under both caffeine and placebo conditions. Throughout the study, researchers will evaluate dopamine D2/D3 receptor availability and brain responses during learning tasks using PET with a radioactive dye and fMRI imaging. The study involves monitoring participants' health, vision, and caffeine habits, as well as safety checks for MRI and PET procedures. The main outcomes include measuring changes in dopamine receptor availability and the effects of caffeine on reinforcement learning performance during the brain scan. Total participation includes the washout periods and scan days under both treatment conditions.

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