Lewis Andrea H, Porcelli Anthony J, Delgado Mauricio R
Department of Psychology, Rutgers University Newark, NJ, USA.
Department of Psychology, Marquette University Milwaukee, WI, USA.
Front Behav Neurosci. 2014 May 22;8:179. doi: 10.3389/fnbeh.2014.00179. eCollection 2014.
Pavlovian conditioning involves the association of an inherently neutral stimulus with an appetitive or aversive outcome, such that the neutral stimulus itself acquires reinforcing properties. Across species, this type of learning has been shown to involve subcortical brain regions such as the striatum and the amygdala. It is less clear, however, how the neural circuitry involved in the acquisition of Pavlovian contingencies in humans, particularly in the striatum, is affected by acute stress. In the current study, we investigate the effect of acute stress exposure on Pavlovian conditioning using monetary reinforcers. Participants underwent a partial reinforcement conditioning procedure in which neutral stimuli were paired with high and low magnitude monetary gains and losses. A between-subjects design was used, such that half of the participants were exposed to cold stress while the remaining participants were exposed to a no stress control procedure. Cortisol measurements and subjective ratings were used as measures of stress. We observed an interaction between stress, valence, and magnitude in the ventral striatum, with the peak in the putamen. More specifically, the stress group exhibited an increased sensitivity to magnitude in the gain domain. This effect was driven by those participants who experienced a larger increase in circulating cortisol levels in response to the stress manipulation. Taken together, these results suggest that acute stress can lead to individual differences in circulating cortisol levels which influence the striatum during Pavlovian conditioning with monetary reinforcers.
经典条件作用涉及将一个原本中性的刺激与一个愉悦或厌恶的结果联系起来，从而使中性刺激本身获得强化特性。在跨物种研究中，这种学习类型已被证明涉及纹状体和杏仁核等皮层下脑区。然而，尚不清楚人类尤其是纹状体中参与习得经典条件性关联的神经回路如何受到急性应激的影响。在本研究中，我们使用金钱强化物来探究急性应激暴露对经典条件作用的影响。参与者接受了部分强化条件作用程序，其中中性刺激与高低金额的金钱收益和损失配对。采用了被试间设计，使得一半的参与者暴露于冷应激，而其余参与者暴露于无应激对照程序。皮质醇测量和主观评分被用作应激指标。我们观察到腹侧纹状体中应激、效价和金额之间存在交互作用，峰值出现在壳核。更具体地说，应激组在收益领域对金额表现出更高的敏感性。这种效应是由那些在应激操作后循环皮质醇水平升高幅度更大的参与者驱动的。综上所述，这些结果表明急性应激可导致循环皮质醇水平的个体差异，这些差异在使用金钱强化物的经典条件作用过程中会影响纹状体。
