title: Delay discounting correlates with proportional lateral frontal cortex volumes.
abstract: BACKGROUND
  Functional neuroimaging experiments in healthy control subjects have shown that choosing between small and immediate rewards versus larger but deferred rewards in delay discounting (DD) tasks recruits mesofrontal and lateral frontal cortex. Might individual differences in frontocortical gray matter morphology be related to preference for immediate reward?
  
  
  METHODS
  We related DD in a laboratory decision-making task to proportional frontocortical gray matter (GM) volumes calculated from segmented magnetic resonance images in 29 healthy adults.
  
  
  RESULTS
  Dorsolateral and inferolateral frontal cortex GM volumes (corrected as a proportion of whole cerebral brain volume) each correlated inversely with preference for immediate gratification during decision making, as indexed by DD constant k. Conversely, neither proportional orbitofrontal or mesofrontal cortex GM volume nor cerebral brain volume (CBV) or total intracranial volume (ICV; a measure of maximal brain growth) significantly correlated with severity of DD.
  
  
  CONCLUSIONS
  Severity of discounting of delayed rewards correlates with proportional lateral frontocortical GM morphology but not with whole brain measures. In light of evidence of frontocortical abnormalities in substance dependence and sociopathy, future studies can assess whether reduced frontocortical volume itself is a morphological marker or risk factor for inability to delay gratification in psychiatric disorders.
authors.affiliation: Division of Clinical Neuroscience and Behavioral Research, National Institute on Drug Abuse, National Institutes of Health, Bethesda, Maryland 20892, USA. jbjork@mail.nih.gov
authors.forename: James M
authors.initials: JM
authors.lastname: Bjork
authors.forename: Reza
authors.initials: R
authors.lastname: Momenan
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Hommer
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000033:anatomy & histology*; D003657:Decision Making; D005260:Female; D005625:Frontal Lobe / Q000033:anatomy & histology*; D006801:Humans; D007175:Impulsive Behavior; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D012201:Reward; D012886:Skull / Q000033:anatomy & histology