Abstract
Normal aging is associated with a decline in different cognitive domains and local structural atrophy as well as decreases in dopamine concentration and receptor density. To date, it is largely unknown how these reductions in dopaminergic neurotransmission affect human brain regions responsible for reward-based decision making in older adults. Using a learning criterion in a probabilistic object reversal task, we found a learning stage by age interaction in the dorsolateral prefrontal cortex (dlPFC) during decision making. While young adults recruited the dlPFC in an early stage of learning reward associations, older adults recruited the dlPFC when reward associations had already been learned. Furthermore, we found a reduced change in ventral striatal BOLD signal in older as compared to younger adults in response to high probability rewards. Our data are in line with behavioral evidence that older adults show altered stimulus–reward learning and support the view of an altered fronto-striatal interaction during reward-based decision making in old age, which contributes to prolonged learning of reward associations.
Highlights
Aging is associated with a decline in different cognitive domains, such as working memory, episodic memory, fluid aspects of intelligence, and executive functioning (Lindenberger et al, 1993; Craik and Salthouse, 2000)
Normal aging is associated with a decline in different cognitive domains and local structural atrophy as well as decreases in dopamine concentration and receptor density
Using a learning criterion in a probabilistic object reversal task, we found a learning stage by age interaction in the dorsolateral prefrontal cortex during decision making
Summary
Aging is associated with a decline in different cognitive domains, such as working memory, episodic memory, fluid aspects of intelligence, and executive functioning (Lindenberger et al, 1993; Craik and Salthouse, 2000). The PFC and basal ganglia appear to be susceptible to age-related decreases in volume (Raz, 2000; Raz and Rodrigue, 2006) Based on these findings, the dopamine hypothesis of cognitive aging states that neurochemical alterations of the dopaminergic system give rise to declines in various cognitive functions in old age (Bäckman et al, 2006). Neurophysiological studies in animals and, more recently, neuroimaging studies in healthy young humans have identified a neural network, which represents different modalities and aspects of reward processing and reward association learning This network includes the dopaminergic midbrain (substantia nigra/ventral tegmental area, SN/VTA) and its target structures such as the PFC [orbitofrontal cortex (OFC), ventromedial and dorsolateral PFC (dlPFC)], the amygdala, and the ventral striatum (VST, Schultz, 2000 for review). Most of these findings are in line with the hypothesis that VST responses signal errors in the prediction of rewards (McClure et al, 2004; Schultz, 2007)
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