Age differences in strategy selection and risk preference during risk-based decision making.

Abstract

Studies of the effects of aging on decision making suggest that choices can be altered in a variety of ways depending on the situation, the nature of the outcome and risk or certainty levels. To better characterize how aging impacts decision making in rodents, young and aged F344 rats underwent a series of probabilistic discounting tasks in which reward magnitude and probabilities were manipulated. Young rats tended to choose one of two different strategies: 1) to press for the large/uncertain reward, regardless of the reward probability; or 2) to continually adapt their behavior according to the odds of winning. The first strategy was adopted by about half of the younger rats, the second by the remaining young animals and the entire group of aged rats. Additionally, we found that when the odds of winning were varied from uncertain to certain during a session, aged rats chose most often the lever associated with the small/certain reward. This is consistent with an interpretation of increased risk aversion. When this behavior was further characterized using a lose-shift analysis, it appears that older rats exhibited an increased sensitivity to negative-feedback. In contrast, sensitivity to wins as well as reward magnitude discrimination was unaltered in aged rats compared to young, suggesting that aging selectively impacts rat’s behavior following losses. In line with some human aging studies, it appears that aged rats are either more risk averse or have a greater certainty bias, which may result from age differences in emotion regulation.

Loss of Sensitivity to Rewards by Dopamine Neurons May Underlie Age-Related Increased Probability Discounting

“…The current data show that aged rats display a decreased choice of the large risky reward, i.e., more discounting on the probability discounting task, reflecting an age-related change in risk-based decision making. Previous reports have not found this same age-related effect on probability discounting in rats (Gilbert et al, 2012;Samson et al, 2015). This apparent discrepancy could be due to rat strain differences, i.e., F344 rats in Gilbert et al (2012) and Samson et al (2015), or a difference in methodologies rather than a lack of an age-related effect on probability discounting.…”

“…Previous reports have not found this same age-related effect on probability discounting in rats (Gilbert et al, 2012;Samson et al, 2015). This apparent discrepancy could be due to rat strain differences, i.e., F344 rats in Gilbert et al (2012) and Samson et al (2015), or a difference in methodologies rather than a lack of an age-related effect on probability discounting. For example, in Gilbert et al (2012), the reward was grain-based rather than sucrose and the large reward was twice the size of the small, vs. four times in our current study.…”

“…We next assessed if age-related changes on risk-based decision making were related to deficits in spatial memory. Previous research suggests that deficits in spatial memory tasks with age can be selective, indicating that age-related decline in the hippocampus happens independently of changes in other brain regions (Gilbert et al, 2012;Samson et al, 2015). To assess this in the current study, individual choice behavior on the probability discounting task was correlated with performance on the water maze.…”

“…In humans, older individuals tend to choose sure gains and avoid sure losses (Mather et al, 2012), avoid risky choices (Lee et al, 2008), and gains and losses are encoded asymmetrically (Samanez-Larkin et al, 2007). However, aging has also been associated with an increase in making risky choices in some rats and humans, and risk-aversion in others (Mata et al, 2011;Gilbert et al, 2012;Samson et al, 2015). The findings of individual differences in probability discounting in aged rats are consistent with evidence for individual differences in aged rat, monkey, and human performance in other cognitive domains (Gallagher et al, 1993(Gallagher et al, , 2011Barense et al, 2002;Schoenbaum et al, 2006;Bizon et al, 2009;Morrison and Baxter, 2012).…”

Cognitive changes across the menopause transition: A longitudinal evaluation of the impact of age and ovarian status on spatial memory

“…Our results, if translated to women, suggest that an earlier onset of transitional menopause may result in disrupted cognition. It is notable that aging affects the functional connectivity and structure of brain areas important for learning and memory (Barnes et al, 1979; Poe et al, 2000) and these changes may impact strategy selection for solving behavioral tasks (Samson et al, 2015). As such, it is a possibility that younger animals relied more heavily on an allocentric spatial strategy to solve the WRAM compared to the strategies used by older animals.…”