Functional imaging of implicit marijuana associations during performance on an Implicit Association Test (IAT)
Susan L Ames1, Jerry L Grenard, Alan W Stacy
1School of Community and Global Health, Claremont Graduate University, Claremont, CA, United States.
Behavioural Brain Research
|September 14, 2013
Summary
Heavy marijuana users exhibit distinct brain activity patterns in the striatum during habit-based memory tasks compared to non-users. This suggests differences in neural pathways for habit formation and controlled behaviors.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Addiction Research
Background:
- Implicit associative memory, particularly habit-based processes, plays a role in drug use.
- Previous research indicates drug-related associative memory effects predict drug use levels.
Purpose of the Study:
- To investigate the neural correlates of implicit associative memory in heavy marijuana users versus non-users.
- To compare brain activity during a marijuana-specific Implicit Association Test (IAT).
Main Methods:
- Functional magnetic resonance imaging (fMRI) was used to scan 13 heavy marijuana users and 15 non-using controls (ages 18-25).
- Participants completed a marijuana Implicit Association Test (IAT) measuring associative memory effects.
- Analysis focused on group by condition interactions in specific brain regions.
Main Results:
- Marijuana users showed greater activity in the dorsal striatum (caudate and putamen) during compatible trials (positive outcomes).
- Non-users exhibited greater activity in the right inferior frontal gyrus during incompatible trials (effortful processing).
- Heavy users displayed striatal and frontal activity during compatible trials, while non-users showed frontal activity during incompatible trials.
Conclusions:
- Findings support a dual process framework for appetitive behaviors.
- Implicit habit-based associations are mediated by striatal neural circuitry.
- Deliberative/controlled behaviors are linked to prefrontal cortex-dependent circuitry.
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