Influences of a DRD2 polymorphism on updating of long-term memory representations and caudate BOLD activity: magnification in aging.

A number of genetic polymorphisms are related to individual differences in cognitive performance. Striatal dopamine (DA) functions, associated with cognitive performance, are linked to the TaqIA polymorphism of the DRD2/ANKK1 gene. In humans, presence of an A1 allele of the DRD2/ANKK1-TaqIA polymorphism is related to reduced density of striatal DA D2 receptors. The resource-modulation hypothesis assumes that aging-related losses of neurochemical and structural brain resources modulate the extent to which genetic variations affect cognitive functioning. Here, we tested this hypothesis using functional MRI during long-term memory (LTM) updating in younger and older carriers and noncarriers of the A1-allele of the TaqIa polymorphism. We demonstrate that older A1-carriers have worse memory performance, specifically during LTM updating, compared to noncarriers. Moreover, A1-carriers exhibited less blood oxygen level-dependent (BOLD) activation in left caudate nucleus, a region critical to updating. This effect was only seen in older adults, suggesting magnification of genetic effects on functional brain activity in aging. Further, a positive relationship between caudate BOLD activation and updating performance among non-A1 carriers indicated that caudate activation was behaviorally relevant. These results demonstrate a link between the DRD2/ANKK1-TaqIA polymorphism and neurocognitive deficits related to LTM updating, and provide novel evidence that this effect is magnified in aging.