Delay discounting correlates with proportional lateral frontal cortex volumes
James M Bjork1, Reza Momenan, Daniel W Hommer
1Division of Clinical Neuroscience and Behavioral Research, National Institute on Drug Abuse, National Institutes of Health, Bethesda, Maryland 20892, USA. jbjork@mail.nih.gov
Biological Psychiatry
|January 6, 2009
Summary
Individual differences in frontocortical gray matter volume are linked to how people make decisions about immediate versus delayed rewards. Reduced lateral frontal cortex gray matter correlates with a stronger preference for immediate gratification.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Neuroimaging
Background:
- Delay discounting (DD) tasks involve choosing between immediate, smaller rewards and delayed, larger rewards.
- Functional neuroimaging shows mesofrontal and lateral frontal cortex activation during DD tasks in healthy individuals.
Purpose of the Study:
- To investigate the relationship between frontocortical gray matter morphology and individual differences in delay discounting.
- To determine if structural brain differences predict preference for immediate rewards.
Main Methods:
- Magnetic resonance imaging (MRI) was used to segment and calculate proportional gray matter (GM) volumes in the frontocortical regions of 29 healthy adults.
- Delay discounting behavior was assessed using a laboratory decision-making task, with the discounting constant (k) as the primary measure.
Main Results:
- Gray matter volumes in the dorsolateral and inferolateral frontal cortex showed an inverse correlation with the preference for immediate gratification (higher k).
- No significant correlations were found between proportional orbitofrontal or mesofrontal cortex GM volume, cerebral brain volume (CBV), or total intracranial volume (ICV) and the severity of delay discounting.
Conclusions:
- Lateral frontocortical gray matter morphology is associated with the severity of delay discounting, but not with overall brain size measures.
- Reduced lateral frontocortical volume may serve as a morphological marker or risk factor for impaired delay of gratification in psychiatric disorders.
