A new brain imaging approach shows how methylphenidate (commonly known as Ritalin), a widely used ADHD medication and off-label "smart pill," affects dopamine and noradrenaline systems differently across individuals. New Radboudumc research, published in Imaging Neuroscience, links the drug’s cognitive effects to a person’s unique brain chemistry, offering clues to why methylphenidate’s effects vary so widely.
Methylphenidate is known to increase dopamine and noradrenaline by blocking their transporters in the brain. Yet it remains unclear how these systems contribute to the drug’s cognitive effects, such as improving focus, learning, and motivation. Traditional neuroimaging methods like fMRI lack the precision to link brain activity to specific neurotransmitters, leaving a critical gap in understanding how psychoactive drugs work.
To address this, researchers from the Motivational & Cognitive Control group at the Department of Psychiatry used REACT (Receptor Enriched Analysis of Connectivity by Targets), a method that combines fMRI data with neurotransmitter receptor maps. This allowed them to link methylphenidate-induced changes in brain activity to specific neurotransmitters. Unlike earlier studies using averaged data, this study used PET scans from the same individuals to validate REACT’s ability to distinguish dopamine from noradrenaline effects. The findings confirm REACT’s potential to reveal how brain chemistry shapes drug effects.
The team analyzed fMRI data using REACT from 85 healthy volunteers who performed a learning task on methylphenidate or placebo. They combined these data with PET scans measuring individual dopamine synthesis capacity. Results showed that methylphenidate altered both dopamine- and noradrenaline-related brain networks, but only dopamine changes correlated with baseline dopamine levels. This suggests that methylphenidate’s effects on dopamine signaling depend on a person’s unique brain chemistry.
The study also found that the dopamine-related changes in the prefrontal cortex, a key region for higher cognitive function, overlapped with brain areas involved in reward processing. This aligns with methylphenidate’s known effects on reward processing, suggesting that the drug enhances prefrontal function by strengthening communication between dopamine-rich subcortical regions and the prefrontal cortex.
These findings by van den Bosch and Cools represent a key advance in molecular-level brain imaging. This study paves the way for more precise drug research that could accelerate drug discovery and improve treatments. For clinicians and researchers, this opens opportunities to collaborate on applying REACT to other drugs or conditions where neurotransmitter systems play a key role, like depression or addiction. In the future, REACT could bridge the gap between non-invasive brain imaging and the molecular mechanisms of psychoactive drugs, ultimately bringing these scientific advances closer to real-world clinical applications.
This research is part of Radboudumc research program: Stress and Mental Health
The Motivational & Cognitive Control research group
About the publication
Ruben van den Bosch, Roshan Cools; Validating molecular target-enriched fMRI for disentangling drug effects on dopamine. Imaging Neuroscience 2026; 4 IMAG.a.1139. doi: https://doi.org/10.1162/IMAG.a.1139
Commentary on this article: https://doi.org/10.1162/IMAG.a.1175
We thank Helena Olraun, PhD candidate in Cools' lab, for her contribution to this piece.
