Habitual behavior after stress: alterations in outcome representations?

工具性学习可以通过目标导向和习惯过程来控制。最近的研究结果表明，急性压力可能会导致从目标导向到习惯性过程的转变。虽然应激后的这种转变也与临床环境高度相关，但这种转变何时发生仍然完全未知。此外，目前存在一个争议，即是否存在从目标导向到习惯学习的训练依赖转变，而不管人类是否有压力。为了解决这些开放性问题，本项目将采用一种新颖的方法：基于目标导向学习和习惯学习在反应产生的结果是否被编码的定义上的不同，该项目将结合多变量解码分析和脑电图（EEG）来评估在呈现歧视性刺激和在长时间学习期间做出反应时行为结果的心理表征。这种方法将首次允许对学习过程中目标导向和习惯过程的动态进行细粒度分析。为了评估压力对这些动态的影响，健康参与者将在执行工具学习任务之前经历标准化的压力或控制程序-同时记录脑电图-在此期间呈现刺激(S)-反应(R)-结果(O)序列，从而实现目标导向（S-R-O）和习惯（S-R）学习。除了具体的脑电图测量，我们将包括具体的试验，其中一个结果是贬值的，这允许在行为层面上分离目标导向和习惯过程，以及眼球追踪。据推测，随着训练的增加，从目标导向到习惯过程的转变，这种转变反映在对行动结果的（神经）表征的减少上。与控制条件相比，压力被认为促进了这种转变，从而导致结果表征减少，特别是在适度训练之后。总而言之，该项目将为人类行为的基本方面提供新的见解：（何时）人类的反应独立于其结果，以及压力如何影响学习过程中控制工具行为的动态？

Instrumental learning can be controlled by a goal-directed and by a habitual process. Recent findings show that acute stress may induce a shift from goal-directed to habitual processes. Although this shift after stress is also highly relevant for clinical settings, it is still completely unknown when this shift occurs. Moreover, there is currently a controversy about whether there is a training-dependent shift from goal-directed to habit learning, irrespective of stress, in humans or not. To address these open questions, the present project will employ a novel approach: based on the idea that goal-directed and habit learning differ per definition in whether the outcome that is engendered by a response is encoded or not, the project will combine multivariate decoding analyses with electroencephalography (EEG) to assess the mental representation of action outcomes during the presentation of discriminative stimuli and during responding across an extended learning session. This approach will allow for the first time a fine-grained analysis of the dynamics of goal-directed and habitual processes across learning. In order to assess the impact of stress on these dynamics, healthy participants will undergo a standardized stress or control procedure before they perform an instrumental learning task - while EEG is recorded - during which stimulus(S)-response(R)-outcome(O) sequences are presented, thus enabling both goal-directed (S-R-O) and habit (S-R) learning. In addition to specific EEG-measures, we will include specific trials in which one outcome is devalued which allows a separation of goal-directed and habit processes at the behavioral level as well as eyetracking. It is hypothesized that there is a shift from goal-directed to habit processes with increased training and that this shift is reflected in a decrease of the (neural) representation of action outcomes. Stress is assumed to facilitate this shift, thus leading to reduced outcome representations, compared to the control condition, in particular after moderate training. In sum, this project will provide novel insights into fundamental aspects of human behavior: (when) does human responding become independent of its outcomes and how does stress affect the dynamics in the control of instrumental behavior across learning?