Neural circuit selective for fast but not slow dopamine increases in drug reward

The faster a drug enters the brain, the greater its addictive potential, yet the brain circuits underlying the rate dependency to drug reward remain unresolved. With simultaneous PET-fMRI we linked dynamics of dopamine signaling, brain activity/connectivity, and self-reported 'high' in 20 adults receiving methylphenidate orally (results in slow delivery) and intravenously (results in fast delivery) (trial NCT03326245). We estimated speed of striatal dopamine increases to oral and IV methylphenidate and then tested where brain activity was associated with slow and fast dopamine dynamics (primary endpoint). We then tested whether these brain circuits were temporally associated with individual 'high' ratings to methylphenidate (secondary endpoint). A corticostriatal circuit comprising the dorsal anterior cingulate cortex and insula and their connections with dorsal caudate was activated by fast (but not slow) dopamine increases and paralleled 'high' ratings. These data provide evidence in humans for a link between dACC/insula activation and fast but not slow dopamine increases and document a critical role of the salience network in drug reward. The faster a drug enters the brain, the greater its addictive potential. Using simultaneous PET-fMRI in humans, here the authors report a neural circuit responding to fast but not slow dopamine increases from intravenous versus oral methylphenidate delivery.

Automated summary

Using simultaneous PET-fMRI, this study reveals a neural circuit in humans that responds to fast dopamine increases caused by intravenous delivery of methylphenidate. The circuit involves the dorsolateral anterior cingulate cortex, insula, and their connections with the dorsal caudate, and it is associated with the subjective experience of 'high' from the drug. The findings highlight the importance of the salience network in drug reward.