Structural brain correlates of delay of gratification in the elderly.
Delay of gratification (DoG) refers to the ability to postpone immediate rewards in favor of later and better rewards. A successful DoG in children/adolescents is subject to the maturation of the lateral and medial prefrontal cortex, which is more prone to normal age-related atrophy compared with other brain regions. Therefore, we investigated morphological brain correlates of DoG using structural MRI surface-based morphometry as well as determined whether dorsolateral prefrontal cortex (DLPFC) atrophy is related to DoG in the elderly. We used the behavioral Delay of Gratification Test for Adults to measure DoG in 40 healthy older adults aged between 63 and 93 years. When simultaneously controlling for age and intracranial volume, high DoG significantly positively correlated with cortical surface area of the left DLPFC. At a more liberal statistical threshold, we found positive correlations between DoG and cortical thickness of the left and right DLPFC, left and right ventrolateral prefrontal cortex, and left midanterior cingulate cortex. Additionally, cortical surface area in the left DLPFC correlated positively with DoG as well as with the volume of the left caudate nucleus. The results suggest that the DLPFC, medial prefrontal cortex, and the caudate nucleus play a crucial role in DoG in the elderly supporting studies in related constructs such as delay discounting and impulsivity. Further, the study shows that age-related prefrontal atrophy is associated with DoG performance. The findings are in line with concepts of "willpower" that postulate a central role of frontostriatal connectivity in self-regulation and self-control.