Age-related changes in risky decision making and associated neural circuitry in a rat model.

Altered decision making at advanced ages can have a significant impact on an individual's quality of life and the ability to maintain personal independence. Relative to young adults, older adults make less impulsive and less risky choices; although these changes in decision making could be considered beneficial, they can also lead to choices with potentially negative consequences (e.g., avoidance of medical procedures). Rodent models of decision making have been invaluable for dissecting cognitive and neurobiological mechanisms that contribute to age-related changes in decision making, but they have predominantly used costs related to timing or probability of reward delivery and have not considered other equally important costs, such as risk of adverse consequences. The current study therefore used a rat model of decision making involving risk of explicit punishment to examine age-related changes in this form of choice behavior in male rats, and to identify potential cognitive and neurobiological mechanisms that contribute to these changes. Relative to young rats, aged rats displayed greater risk aversion, which was not attributable to reduced motivation for food, changes in shock sensitivity, or impaired cognitive flexibility. Functional MRI analyses revealed that overall, functional connectivity was greater in aged rats compared with young rats, particularly among brain regions implicated in risky decision making such as basolateral amygdala, orbitofrontal cortex, and ventral tegmental area. Collectively, these findings are consistent with greater risk aversion found in older humans, and reveal age-related changes in brain connectivity. SIGNIFICANCE STATEMENT Changes in cost-benefit decision making at advanced ages can be modeled in rats. Although such models have largely corroborated age changes in some forms of decision making, they have not evaluated decisions involving risks of adverse consequences (i.e., punishment). The current study evaluated young and aged rats in a decision making task involving risk of punishment. As in humans, aged rats were more risk averse than young. This greater risk aversion was accompanied by greater functional connectivity among brain regions implicated in risky decision making. The findings suggest that greater risk aversion in aging is due to inherent (biological) factors, and establish a model in which future work can evaluate neural mechanisms underlying age-related changes in risk taking.