F206. Neural Mechanisms Guiding Choices for Cannabis and Alternative Rewards in Cannabis Smokers
Section snippets
Background
Substance misuse is characterised by persistent choices for drugs over other rewards. Neural mechanisms underpinning drug-biased choice in humans are poorly understood. Using an experimental medicine approach, we investigated subjective value (SV) encoding during choices for cannabis and a natural reward (individuals’ preferred snacks) in regular cannabis smokers. Effects of cues (cannabis, snack, or neutral) were also assessed.
Methods
Near-daily cannabis smokers (N = 20; 1 female) completed a 6-day, within-subject, inpatient protocol. After sampling the reinforcers (6 cannabis puffs; 6 small snacks), they completed 4 conditions: 1. Neutral cues/cannabis choices; 2. Cannabis cues/cannabis choices; 3. Neutral cues/snack choices; and 4. Snack cues/snack choices. In each, participants were exposed to cues before an fMRI scan during which they chose repeatedly between 0-6 cannabis puffs/snacks and an individualized monetary
Results
There was no effect of cues or interaction between cues and reinforcer type on SV encoding. SVs for cannabis correlated with activation in regions previously shown to encode value for other rewards, including ventromedial Prefrontal Cortex (vmPFC); a similar pattern was not observed during snack choices. Value encoding in vmPFC was greater for cannabis than snack food (Small Volume Correction; p<0.05).
Conclusions
Cannabis smokers had intact value encoding for cannabis but disrupted encoding of non-drug value, consistent with models identifying dysregulated valuation of drug relative to alternative reinforcers as a driver of problematic substance use.
Supported By
NIDA: DA034877; DA044339
Keywords
Neuroeconomics, Cannabis, Subjective Value, Experimental Medicine, Human Behavioral Pharmacology