Tryon Valerie L, Baker Phillip M, Long Jeffrey M, Rapp Peter R, Mizumori Sheri J Y
Department of Psychology, University of Washington, Seattle, WA, United States.
Laboratory of Behavioral Neuroscience, Neurocognitive Aging Section, National Institute on Aging, National Institutes of Health, Baltimore, MD, United States.
Front Aging Neurosci. 2020 Mar 6;12:49. doi: 10.3389/fnagi.2020.00049. eCollection 2020.
Normative aging is known to affect how decisions are made in risky situations. Although important individual variability exists, on average, aging is accompanied by greater risk aversion. Here the behavioral and neural mechanisms of greater risk aversion were examined in young and old rats trained on an instrumental probability discounting task. Consistent with the literature, old rats showed greater discounting of reward value when the probability of obtaining rewards dropped below 100%. Behaviorally, reward magnitude discrimination was the same between young and old rats, and yet these same rats exhibited reduced sensitivity to positive, but not negative, choice outcomes. The latter behavioral result was congruent with additional findings that the aged ventral tegmental neurons (including dopamine cells) were less responsive to rewards when compared to the same cell types recorded from young animals. In sum, it appears that reduced responses of dopamine neurons to rewards contribute to aging-related changes in risky decisions.
众所周知，正常衰老会影响在风险情境中做出决策的方式。尽管存在重要的个体差异，但平均而言，衰老伴随着更强的风险规避。在此，我们在接受工具性概率折扣任务训练的年轻和老年大鼠中研究了更强风险规避的行为和神经机制。与文献一致，当获得奖励的概率降至100%以下时，老年大鼠对奖励价值的折扣更大。行为上，年轻和老年大鼠之间的奖励幅度辨别相同，但这些大鼠对积极而非消极的选择结果表现出较低的敏感性。后一行为结果与其他研究结果一致，即与从年轻动物记录的相同细胞类型相比，老年腹侧被盖区神经元（包括多巴胺能细胞）对奖励的反应较弱。总之，多巴胺神经元对奖励的反应降低似乎导致了与衰老相关的风险决策变化。
