Center for Neural Science and Department of Psychology, New York University, New York, NY 10003.
Proc Natl Acad Sci U S A. 2013 Dec 24;110(52):20941-6. doi: 10.1073/pnas.1312011110. Epub 2013 Dec 9.
Accounts of decision-making have long posited the operation of separate, competing valuation systems in the control of choice behavior. Recent theoretical and experimental advances suggest that this classic distinction between habitual and goal-directed (or more generally, automatic and controlled) choice may arise from two computational strategies for reinforcement learning, called model-free and model-based learning. Popular neurocomputational accounts of reward processing emphasize the involvement of the dopaminergic system in model-free learning and prefrontal, central executive-dependent control systems in model-based choice. Here we hypothesized that the hypothalamic-pituitary-adrenal (HPA) axis stress response--believed to have detrimental effects on prefrontal cortex function--should selectively attenuate model-based contributions to behavior. To test this, we paired an acute stressor with a sequential decision-making task that affords distinguishing the relative contributions of the two learning strategies. We assessed baseline working-memory (WM) capacity and used salivary cortisol levels to measure HPA axis stress response. We found that stress response attenuates the contribution of model-based, but not model-free, contributions to behavior. Moreover, stress-induced behavioral changes were modulated by individual WM capacity, such that low-WM-capacity individuals were more susceptible to detrimental stress effects than high-WM-capacity individuals. These results enrich existing accounts of the interplay between acute stress, working memory, and prefrontal function and suggest that executive function may be protective against the deleterious effects of acute stress.
长期以来，关于决策的描述都假设在控制选择行为时存在独立的、相互竞争的价值系统。最近的理论和实验进展表明，这种习惯性和目标导向（或更普遍地说，自动和受控）选择之间的经典区别可能源于强化学习的两种计算策略，分别称为无模型学习和基于模型的学习。关于奖励处理的流行神经计算解释强调了多巴胺系统在无模型学习中的参与，以及前额叶、中央执行依赖控制系统在基于模型的选择中的参与。在这里，我们假设下丘脑-垂体-肾上腺（HPA）轴应激反应——被认为对前额叶皮层功能有不利影响——应该选择性地减弱行为的基于模型的贡献。为了验证这一点，我们将急性应激源与一个序列决策任务配对，该任务可以区分两种学习策略的相对贡献。我们评估了基线工作记忆（WM）能力，并使用唾液皮质醇水平来衡量 HPA 轴应激反应。我们发现，应激反应减弱了基于模型的贡献，但没有减弱基于模型的贡献。此外，应激引起的行为变化受到个体 WM 能力的调节，因此低 WM 能力的个体比高 WM 能力的个体更容易受到应激的不利影响。这些结果丰富了关于急性应激、工作记忆和前额叶功能之间相互作用的现有解释，并表明执行功能可能对急性应激的有害影响具有保护作用。
