title: Effects of frequent cannabis use on hippocampal activity during an associative memory task.
abstract: Interest is growing in the neurotoxic potential of cannabis on human brain function. We studied non-acute effects of frequent cannabis use on hippocampus-dependent associative memory, investigated with functional Magnetic Resonance Imaging (fMRI) in 20 frequent cannabis users and 20 non-users matched for age, gender and IQ. Structural changes in the (para)hippocampal region were measured using voxel-based morphometry (VBM). Cannabis users displayed lower activation than non-users in brain regions involved in associative learning, particularly in the (para)hippocampal regions and the right dorsolateral prefrontal cortex, despite normal performance. VBM-analysis of the (para)hippocampal regions revealed no differences in brain tissue composition between cannabis users and non-users. No relation was found between (para)hippocampal tissue composition and the magnitude of brain activity in the (para)hippocampal area. Therefore, lower brain activation may not signify neurocognitive impairment, but could be the expression of a non-cognitive variable related to frequent cannabis use, for example changes in cerebral perfusion or differences in vigilance.
authors.affiliation: Rudolf Magnus Institute of Neuroscience, Department of Psychiatry, A.01.126, University Medical Center, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. gjager@umcutrecht.nl
authors.forename: Gerry
authors.initials: G
authors.lastname: Jager
authors.forename: Hendrika H
authors.initials: HH
authors.lastname: Van Hell
authors.forename: Maartje M L
authors.initials: MM
authors.lastname: De Win
authors.forename: Rene S
authors.initials: RS
authors.lastname: Kahn
authors.forename: Wim
authors.initials: W
authors.lastname: Van Den Brink
authors.forename: Jan M
authors.initials: JM
authors.lastname: Van Ree
authors.forename: Nick F
authors.initials: NF
authors.lastname: Ramsey
mesh_terms: D000328:Adult; D001245:Association Learning / Q000187:drug effects / Q000502:physiology*; D001931:Brain Mapping; D016022:Case-Control Studies; D005260:Female; D006624:Hippocampus / Q000098:blood supply* / Q000503:physiopathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D002189:Marijuana Abuse / Q000473:pathology / Q000503:physiopathology*; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology*; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood
chemical_list: D010100:Oxygen