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The Journal of Neuroscience, December 26, 2007, 27(52):14383-14391; doi:10.1523/JNEUROSCI.2551-07.2007
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Behavioral/Systems/Cognitive
Immediate Reward Bias in Humans: Fronto-Parietal Networks and a Role for the Catechol-O-Methyltransferase 158Val/Val Genotype
Charlotte A. Boettiger,1,2,3 Jennifer M. Mitchell,1 Venessa C. Tavares,1 Margaret Robertson,1 Geoff Joslyn,1 Mark D'Esposito,4 andHoward L. Fields1,2 1Ernest Gallo Clinic and Research Center, Emeryville, California 94608, 2Department of Neurology, University of California, San Francisco, San Francisco, California 94143, 3Department of Psychology, Biomedical Research Imaging Center, and Curriculum in Neurobiology, University of North Carolina, Chapel Hill, North Carolina 27599-3270, and 4Helen Wills Neuroscience Institute and Department of Psychology, University of California, Berkeley, California 94720
Correspondence should be addressed to Dr. Charlotte A. Boettiger, Department of Psychology, Davie Hall, CB#3270, University of North Carolina, Chapel Hill, NC 27599-3270. Email: cab{at}unc.edu
The tendency to choose lesser immediate benefits over greater long-term benefits characterizes alcoholism and other addictive disorders. However, despite its medical and socioeconomic importance, little is known about its neurobiological mechanisms. Brain regions that are activated when deciding between immediate or delayed rewards have been identified (McClure et al., 2004, 2007), as have areas in which responses to reward stimuli predict a paper-and-pencil measure of temporal discounting (Hariri et al., 2006). These studies assume "hot" and "cool" response selection systems, with the hot system proposed to generate impulsive choices in the presence of a proximate reward. However, to date, brain regions in which the magnitude of activity during decision making reliably predicts intertemporal choice behavior have not been identified. Here we address this question in sober alcoholics and non-substance-abusing control subjects and show that immediate reward bias directly scales with the magnitude of functional magnetic resonance imaging bold oxygen level-dependent (BOLD) signal during decision making at sites within the posterior parietal cortex (PPC), dorsal prefrontal cortex (dPFC), and rostral parahippocampal gyrus regions. Conversely, the tendency of an individual to wait for a larger, delayed reward correlates directly with BOLD signal in the lateral orbitofrontal cortex. In addition, genotype at the Val158Met polymorphism of the catechol-O-methyltransferase gene predicts both impulsive choice behavior and activity levels in the dPFC and PPC during decision making. These genotype effects remained significant after controlling for alcohol abuse history. These results shed new light on the neurobiological underpinnings of temporal discounting behavior and identify novel behavioral and neural consequences of genetic variation in dopamine metabolism.
Key words: alcoholism; decision making; delay discounting; fMRI; impulsivity; orbitofrontal
Received June 6, 2007; revised Nov. 7, 2007; accepted Nov. 15, 2007.
Correspondence should be addressed to Dr. Charlotte A. Boettiger, Department of Psychology, Davie Hall, CB#3270, University of North Carolina, Chapel Hill, NC 27599-3270. Email: cab{at}unc.edu
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