title: COMT Val158Met polymorphism, cognitive stability and cognitive flexibility: an experimental examination.
abstract: BACKGROUND
  Dopamine in prefrontal cortex (PFC) modulates core cognitive processes, notably working memory and executive control. Dopamine regulating genes and polymorphisms affecting PFC--including Catechol-O-Methyltransferase (COMT) Val158Met--are crucial to understanding the molecular genetics of cognitive function and dysfunction. A mechanistic account of the COMT Val158Met effect associates the Met allele with increased tonic dopamine transmission underlying maintenance of relevant information, and the Val allele with increased phasic dopamine transmission underlying the flexibility of updating new information. Thus, consistent with some earlier work, we predicted that Val carriers would display poorer performance when the maintenance component was taxed, while Met carriers would be less efficient when rapid updating was required.
  
  
  METHODS
  Using a Stroop task that manipulated level of required cognitive stability and flexibility, we examined reaction time performance of patients with schizophrenia (n = 67) and healthy controls (n = 186) genotyped for the Val/Met variation.
  
  
  RESULTS
  In both groups we found a Met advantage for tasks requiring cognitive stability, but no COMT effect when a moderate level of cognitive flexibility was required, or when a conflict cost measure was calculated.
  
  
  CONCLUSIONS
  Our results do not support a simple stability/flexibility model of dopamine COMT Val/Met effects and suggest a somewhat different conceptualization and experimental operationalization of these cognitive components.
authors.affiliation: Clinical Brain Disorders Branch, National Institute of Mental Heath/National Institutes of Health, 10 Center Drive, MSC 1379, Bethesda, MD 20892, USA.
authors.forename: Elise C
authors.initials: EC
authors.lastname: Rosa
authors.forename: Dwight
authors.initials: D
authors.lastname: Dickinson
authors.forename: José
authors.initials: J
authors.lastname: Apud
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Weinberger
authors.forename: Brita
authors.initials: B
authors.lastname: Elvevåg
mesh_terms: D000328:Adult; D000483:Alleles; D002394:Catechol O-Methyltransferase / Q000235:genetics*; D003071:Cognition; D005260:Female; D006801:Humans; D008297:Male; D011110:Polymorphism, Genetic; D011930:Reaction Time / Q000235:genetics*; D012559:Schizophrenia / Q000235:genetics*; D012565:Schizophrenic Psychology
chemical_list: D002394:Catechol O-Methyltransferase