Gilbert Ryan J, Mitchell Marci R, Simon Nicholas W, Bañuelos Cristina, Setlow Barry, Bizon Jennifer L
Department of Neuroscience, University of Florida College of Medicine Gainesville, FL, USA.
Front Neurosci. 2012 Jan 3;5:144. doi: 10.3389/fnins.2011.00144. eCollection 2011.
Impaired decision-making in aging can directly impact factors (financial security, health care) that are critical to maintaining quality of life and independence at advanced ages. Naturalistic rodent models mimic human aging in other cognitive domains, and afford the opportunity to parse the effects of age on discrete aspects of decision-making in a manner relatively uncontaminated by experiential factors. Young adult (5-7 months) and aged (23-25 months) male F344 rats were trained on a probability discounting task in which they made discrete-trial choices between a small certain reward (one food pellet) and a large but uncertain reward (two food pellets with varying probabilities of delivery ranging from 100 to 0%). Young rats chose the large reward when it was associated with a high probability of delivery and shifted to the small but certain reward as probability of the large reward decreased. As a group, aged rats performed comparably to young, but there was significantly greater variance among aged rats. One subgroup of aged rats showed strong preference for the small certain reward. This preference was maintained under conditions in which large reward delivery was also certain, suggesting decreased sensitivity to reward magnitude. In contrast, another subgroup of aged rats showed strong preference for the large reward at low probabilities of delivery. Interestingly, this subgroup also showed elevated preference for probabilistic rewards when reward magnitudes were equalized. Previous findings using this same aged study population described strongly attenuated discounting of delayed rewards with age, together suggesting that a subgroup of aged rats may have deficits associated with accounting for reward costs (i.e., delay or probability). These deficits in cost-accounting were dissociable from the age-related differences in sensitivity to reward magnitude, suggesting that aging influences multiple, distinct mechanisms that can impact cost-benefit decision-making.
衰老过程中决策能力受损会直接影响对维持老年生活质量和独立性至关重要的因素（金融安全、医疗保健）。自然主义啮齿动物模型在其他认知领域模拟人类衰老，并提供了一个机会，以一种相对不受经验因素影响的方式剖析年龄对决策离散方面的影响。将年轻成年（5 - 7个月）和老年（23 - 25个月）雄性F344大鼠训练进行概率折扣任务，在此任务中它们在一个小而确定的奖励（一粒食物颗粒）和一个大但不确定的奖励（两粒食物颗粒，其交付概率从100%到0%不等）之间进行离散试验选择。年轻大鼠在大奖励与高交付概率相关时选择大奖励，随着大奖励概率降低则转向小但确定的奖励。作为一个群体，老年大鼠的表现与年轻大鼠相当，但老年大鼠之间的差异显著更大。老年大鼠的一个亚组对小而确定的奖励表现出强烈偏好。在大奖励交付也确定的条件下，这种偏好仍然存在，表明对奖励大小的敏感性降低。相比之下，老年大鼠的另一个亚组在低交付概率时对大奖励表现出强烈偏好。有趣的是，当奖励大小相等时，这个亚组对概率奖励的偏好也有所增加。以前使用相同老年研究群体的研究结果描述了随着年龄增长对延迟奖励的折扣大幅减弱，共同表明老年大鼠的一个亚组可能存在与考虑奖励成本（即延迟或概率）相关的缺陷。这些成本核算方面的缺陷与年龄相关的对奖励大小敏感性差异是可分离的，表明衰老影响多种不同的机制，这些机制会影响成本效益决策。
