2014年5月15日木曜日

Working-memory capacity protects model-based learning from stress

A. Ross Otto, Candace M. Raio, Alice Chiang, Elizabeth A. Phelps, and Nathaniel D. Daw
PNAS December 24, 2013 vol. 110 no. 52 20941-20946

モデル・ベースド強化学習とモデル・フリー強化学習。
ヒトは両方を併用していることが知られているが、被験者にストレスを与えるとモデル・ベースド強化学習を使わなくなる。
また、その効果はワークングメモリー能力の低い被験者に顕著だった。

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.

0 件のコメント:

コメントを投稿