title: Cannabis use and memory brain function in adolescent boys: a cross-sectional multicenter functional magnetic resonance imaging study.
abstract: OBJECTIVE
  Early-onset cannabis use has been associated with later use/abuse, mental health problems (psychosis, depression), and abnormal development of cognition and brain function. During adolescence, ongoing neurodevelopmental maturation and experience shape the neural circuitry underlying complex cognitive functions such as memory and executive control. Prefrontal and temporal regions are critically involved in these functions. Maturational processes leave these brain areas prone to the potentially harmful effects of cannabis use.
  
  
  METHODS
  We performed a two-site (United States and The Netherlands; pooled data) functional magnetic resonance imaging (MRI) study with a cross-sectional design, investigating the effects of adolescent cannabis use on working memory (WM) and associative memory (AM) brain function in 21 abstinent but frequent cannabis-using boys (13-19) years of age and compared them with 24 nonusing peers. Brain activity during WM was assessed before and after rule-based learning (automatization). AM was assessed using a pictorial hippocampal-dependent memory task.
  
  
  RESULTS
  Cannabis users performed normally on both memory tasks. During WM assessment, cannabis users showed excessive activity in prefrontal regions when a task was novel, whereas automatization of the task reduced activity to the same level in users and controls. No effect of cannabis use on AM-related brain function was found.
  
  
  CONCLUSIONS
  In adolescent cannabis users, the WM system was overactive during a novel task, suggesting functional compensation. Inefficient WM recruitment was not related to a failure in automatization but became evident when processing continuously changing information. The results seem to confirm the vulnerability of still developing frontal lobe functioning for early-onset cannabis use.
authors.affiliation: Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, The Netherlands. gjager@umcutrecht.nl
authors.forename: Gerry
authors.initials: G
authors.lastname: Jager
authors.forename: Robert I
authors.initials: RI
authors.lastname: Block
authors.forename: Maartje
authors.initials: M
authors.lastname: Luijten
authors.forename: Nick F
authors.initials: NF
authors.lastname: Ramsey
mesh_terms: D000293:Adolescent; D001245:Association Learning / Q000187:drug effects* / Q000502:physiology; D001288:Attention / Q000187:drug effects / Q000502:physiology; D019955:Conduct Disorder / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology; D003430:Cross-Sectional Studies; D056344:Executive Function / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology / Q000503:physiopathology* / Q000523:psychology*; D008385:Marijuana Smoking / Q000009:adverse effects* / Q000453:epidemiology / Q000503:physiopathology / Q000523:psychology; D008570:Memory, Short-Term / Q000187:drug effects* / Q000502:physiology; D009483:Neuropsychological Tests; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000503:physiopathology; D011594:Psychometrics