fMRI response to spatial working memory in adolescents with comorbid marijuana and alcohol use disorders

Abstract

Alcohol and marijuana use are prevalent in adolescence, yet the neural impact of concomitant use remains unclear. We previously demonstrated functional magnetic resonance imaging (fMRI) response to spatial working memory (SWM) among teens with alcohol use disorders (AUD) compared to controls, and predicted that adolescents with marijuana and alcohol use disorders would show additional abnormalities.Participants were three groups of 15−17-year-olds: 19 non-abusing controls, 15 AUD teens with limited exposure to drugs, and 15 teens with comorbid marijuana and alcohol use disorders (MAUD) and minimal other drug experience. After >2 days' abstinence, participants performed a SWM task during fMRI acquisition. fMRI brain response patterns differed between groups, despite similar performance on the task. MAUD youths showed less activation in inferior frontal and temporal regions than controls, and more response in other prefrontal regions. Compared to AUD teens, MAUD youths also showed less inferior frontal and temporal activation, but more medial frontal response. Overall, MAUD youths showed different brain response abnormalities than teens with AUD alone, despite relatively short histories of substance involvement. This pattern could suggest compensation for marijuana-related attention and working memory deficits. However, relatively recent use and premorbid features may influence results, and should be examined in future studies.

Abstinent adolescent marijuana users show altered fMRI response during spatial working memory

“…In contrast, our previous work revealed increased SWM response in this region among heavy alcohol-and marijuana-using teens who had been abstinent an average of just 8 days (Schweinsburg et al, 2005b). Kanayama and colleagues (Kanayama et al, 2004) also observed greater dorsolateral prefrontal response among adult heavy marijuana users on a similar SWM task 6-36 h after marijuana use.…”

“…Research on parietal functioning during working memory among individuals with substance use disorders has been somewhat inconsistent. Using the same SWM task, we previously failed to observe parietal abnormalities among adolescent users of alcohol and marijuana (Schweinsburg et al, 2005b), though teens with alcohol use disorders alone showed increased posterior parietal brain response compared with controls (Tapert et al, 2004) despite similar task performance between groups. Greater fMRI activation in posterior parietal cortex has also been observed during SWM among adult marijuana users (Kanayama et al, 2004) as well as during verbal working memory among adolescent marijuana users experiencing nicotine withdrawal (Jacobsen et al, 2007).…”

“…Interested teens and a parent provided informed assent and consent (for 18-yearolds, the youth provided consent and the parent consented to a collateral informant interview), approved by the University of California San Diego Human Research Protection Program. Each adolescent and a parent were separately administered detailed screening interviews (Tapert et al, 2003;Schweinsburg et al, 2005b). The computerized NIMH Diagnostic Interview Schedule for Children Predictive Scales (DISC-PS-4.32b) (Shaffer et al, 2000;Lucas et al, 2001) excluded adolescents with a psychiatric disorder (including conduct disorder, attention deficit-hyperactivity disorder, and other drug use disorders) based on youth or parent report.…”

“…After an average of 8 days of abstinence, adolescents with comorbid marijuana and alcohol use disorders showed brain response abnormalities not evidenced by those with alcohol use disorders alone, including increased dorsolateral prefrontal activation and reduced inferior frontal response, suggesting compensatory working memory and attention activity associated with heavy marijuana use during youth (Schweinsburg et al, 2005b). Yet it is unclear whether these abnormalities are solely a function of recent use or would be present after a longer period of abstinence, suggesting persistent effects.…”

“…Blood-oxygen-leveldependent (BOLD) fMRI was obtained during an SWM task that typically activates bilateral prefrontal and posterior parietal networks in adolescents (Schweinsburg et al, 2005a), and has been associated with neural dysfunction among youths with alcohol use disorders (Tapert et al, 2004) as well as comorbid alcohol and marijuana use disorders (Schweinsburg et al, 2005b). We predicted that after 28 days of monitored abstinence, marijuana-using teens would demonstrate intact performance on the SWM task yet increased brain response in frontal and parietal regions.…”