title: Effects of methylphenidate on working memory functioning in children with attention deficit/hyperactivity disorder.
abstract: OBJECTIVE
  Children with attention deficit/hyperactivity disorder (ADHD) often show deficits in working memory performance. Methylphenidate (MPH) is an effective medication to improve these cognitive difficulties. This study aimed to clarify which effect MPH induces on the underlying functional networks of working memory.
  
  
  METHODS
  Fourteen boys diagnosed with ADHD and 12 healthy controls were investigated using functional magnetic resonance imaging (fMRI). Each patient was tested twice, once with medication and once without. The fMRI experiments consisted of three verbal N-back tasks with increasing difficulty. Functional images were acquired on a 3 Tesla head scanner.
  
  
  RESULTS
  On the behavioral level, medicated patients performed similar to healthy controls and significantly better than without medication. On the functional level, patients showed the expected frontal and parietal activations, which were more pronounced in the 2- and 3-back tasks. Healthy controls showed significantly more activation in these regions and additional activation in the cerebellum. Interestingly, patients showed an additional effect of laterality. Left-sided frontal and parietal activation in patients was significantly less pronounced than in controls.
  
  
  CONCLUSIONS
  Functional data indicate different activation patterns in verbal working memory tasks between healthy controls and patients with ADHD irrespective of medication condition. Intake of MPH led to a clear improvement on a behavioral level. However, this effect was not reflected by changes in functional brain organization. MPH-induced changes leading to better performance in verbal working memory tasks might be very subtle and therefore not detectable by fMRI.
authors.affiliation: Department of Cognitive Psychology and Methodology, University of Basel, Basel, Switzerland. maja.kobel@unibas.ch
authors.forename: Maja
authors.initials: M
authors.lastname: Kobel
authors.forename: Nina
authors.initials: N
authors.lastname: Bechtel
authors.forename: Peter
authors.initials: P
authors.lastname: Weber
authors.forename: Karsten
authors.initials: K
authors.lastname: Specht
authors.forename: Markus
authors.initials: M
authors.lastname: Klarhöfer
authors.forename: Klaus
authors.initials: K
authors.lastname: Scheffler
authors.forename: Klaus
authors.initials: K
authors.lastname: Opwis
authors.forename: Iris-Katharina
authors.initials: IK
authors.lastname: Penner
mesh_terms: D000704:Analysis of Variance; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications* / Q000175:diagnosis / Q000188:drug therapy; D000697:Central Nervous System Stimulants / Q000494:pharmacology* / Q000627:therapeutic use*; D002648:Child; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis / Q000188:drug therapy* / Q000209:etiology*; D008570:Memory, Short-Term / Q000187:drug effects*; D008774:Methylphenidate / Q000494:pharmacology* / Q000627:therapeutic use*; D009483:Neuropsychological Tests
chemical_list: D000697:Central Nervous System Stimulants; D008774:Methylphenidate