title: A validation of event-related FMRI comparisons between users of cocaine, nicotine, or cannabis and control subjects.
abstract: OBJECTIVE
  Noninvasive brain imaging techniques are a powerful tool for researching the effects of drug abuse on brain activation measures. However, because many drugs have direct vascular effects, the validity of techniques that depend on blood flow measures as a reflection of neuronal activity may be called into question. This may be of particular concern in event-related functional magnetic resonance imaging (fMRI), where current analytic techniques search for a specific shape in the hemodynamic response to neuronal activity.
  
  
  METHODS
  To investigate possible alterations in task-related activation as a result of drug abuse, fMRI scans were conducted on subjects in four groups as they performed a simple event-related finger-tapping task: users of cocaine, nicotine, or cannabis and control subjects.
  
  
  RESULTS
  Activation measures, as determined by two different analytic methods, did not differ between the groups. A comparison between an intravenous saline and an intravenous cocaine condition in cocaine users found a similar null result. Further in-depth analyses of the shape of the hemodynamic responses in each group also showed no differences.
  
  
  CONCLUSIONS
  This study demonstrates that drug groups may be compared with control subjects using event-related fMRI without the need for any post hoc procedures to correct for possible drug-induced cardiovascular alterations. Thus, fMRI activation differences reported between these drug groups can be more confidently interpreted as reflecting neuronal differences.
authors.affiliation: Department of Psychology, Trinity College Dublin, Dublin 2, Ireland. hugh.garavan@tcd.ie
authors.forename: Kevin
authors.initials: K
authors.lastname: Murphy
authors.forename: Veronica
authors.initials: V
authors.lastname: Dixon
authors.forename: Kathleen
authors.initials: K
authors.lastname: LaGrave
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Kaufman
authors.forename: Robert
authors.initials: R
authors.lastname: Risinger
authors.forename: Alan
authors.initials: A
authors.lastname: Bloom
authors.forename: Hugh
authors.initials: H
authors.lastname: Garavan
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply* / Q000503:physiopathology*; D001931:Brain Mapping; D003042:Cocaine / Q000494:pharmacology; D019970:Cocaine-Related Disorders / Q000175:diagnosis* / Q000503:physiopathology; D013759:Dronabinol / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000098:blood supply / Q000503:physiopathology; D006179:Gyrus Cinguli / Q000098:blood supply / Q000503:physiopathology; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D008297:Male; D002189:Marijuana Abuse / Q000175:diagnosis* / Q000503:physiopathology; D008875:Middle Aged; D009538:Nicotine / Q000494:pharmacology; D011597:Psychomotor Performance / Q000502:physiology; D012372:ROC Curve; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D015203:Reproducibility of Results; D014029:Tobacco Use Disorder / Q000175:diagnosis* / Q000503:physiopathology
chemical_list: D009538:Nicotine; D013759:Dronabinol; D003042:Cocaine