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Brain Behav. 2012 September; 2(5): 553–562.
Published online 2012 July 16. doi:  10.1002/brb3.74
PMCID: PMC3489808
The association between cingulate cortex glutamate concentration and delay discounting is mediated by resting state functional connectivity
Lianne Schmaal,1 Anna E Goudriaan,1,2 Johan Meer,3 Wim Brink,1 and Dick J Veltman1,4
1Amsterdam Institute for Addiction Research, Department of Psychiatry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
2Arkin Mental Health Institute, Amsterdam, The Netherlands
3Department of Sleep and Cognition, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
4Department of Psychiatry, VU university medical center, Amsterdam, The Netherlands
Lianne Schmaal, Department of Psychiatry, Academic Medical Center, University of Amsterdam, P.O. Box 22660, 1100 DD Amsterdam, The Netherlands. Tel: +0031 20 8913762; Fax: +0031 20 8913701; E-mail: lianschmaal/at/gmail.com
Funding Information This work was supported by the Netherlands Organization for Scientific Research (ZonMW grant 31160003).
Received May 25, 2012; Accepted June 4, 2012.
Abstract
Humans vary in their ability to delay gratification and impulsive decision making is a common feature in various psychiatric disorders. The level of delay discounting is a relatively stable psychological trait, and therefore neural processes implicated in delay discounting are likely to be based on the overall functional organization of the brain (under task-free conditions) in which state-dependent shifts from baseline levels occur. The current study investigated whether delay discounting can be predicted by intrinsic properties of brain functioning. Fourteen healthy male subjects performed a delay discounting task. In addition, resting state functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy (¹H MRS) were used to investigate the relationship between individual differences in delay discounting and molecular and regional measures of resting state (baseline) activity of dorsal anterior cingulate cortex (dACC). Results showed that delay discounting was associated with both dACC glutamate concentrations and resting state functional connectivity of the dACC with a midbrain region including ventral tegmental area and substantia nigra. In addition, a neural pathway was established, showing that the effect of glutamate concentrations in the dACC on delay discounting is mediated by functional connectivity of the dACC with the midbrain. The current findings are important to acknowledge because spontaneous intrinsic brain processes have been proposed to be a potential promising biomarker of disease and impulsive decision making is associated with several psychiatric disorders.
Keywords: Anterior cingulate cortex, delay discounting, glutamate, impulsive decision making, magnetic resonance spectroscopy, resting state fMRI
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