The Influence of Recency of Use on fMRI Response During Spatial Working Memory in Adolescent Marijuana Users

摘要

Some neurocognitive recovery occurs within a month of abstinence from heavy marijuana use, yet functional magnetic resonance imaging (fMRI) has revealed altered activation among recent and abstinent adult users. Here, we compared fMRI response during a spatial working memory (SWM) task between adolescent marijuana users with brief and sustained durations of abstinence.Participants were 13 recent users (2 – 7 days abstinent), 13 abstinent users (27 – 60 days abstinent), and 18 non-using controls, all ages 15 – 18. Groups were similar on demographics, had no psychiatric or medical disorders, and user groups were similar on substance histories. Teens performed a 2-back SWM task during fMRI.Groups performed similarly on the task, but recent users showed greater fMRI response in medial and left superior prefrontal cortices, as well as bilateral insula. Abstinent users had increased response in the right precentral gyrus (clusters ≥1328 μl, p<.05).This cross-sectional study did not examine changes in brain response among the same participants over time. Yet results suggests that adolescents who recently used marijuana show increased brain activity in regions associated with working memory updating and inhibition, compared to users with weeks to months of abstinence. This study preliminarily suggests that (1) recent marijuana use may disrupt neural connections associated with SWM and result in compensatory brain response, and (2) sustained abstinence from marijuana may be associated with improvements in SWM response among adolescents.