Shumake Jason, Monfils Marie H
Department of Psychology, The University of Texas at Austin Austin, TX, USA.
Front Behav Neurosci. 2015 Dec 23;9:355. doi: 10.3389/fnbeh.2015.00355. eCollection 2015.
Freezing has become the predominant measure used in rodent studies of conditioned fear, but conditioned suppression of reward-seeking behavior may provide a measure that is more relevant to human anxiety disorders; that is, a measure of how fear interferes with the enjoyment of pleasurable activities. Previous work has found that an isolated presentation of a fear conditioned stimulus (CS) prior to extinction training (retrieval + extinction) results in a more robust and longer-lasting reduction in fear. The objective of this study was to assess whether the retrieval + extinction effect is evident using conditioned suppression of reward seeking, operationalized as a reduction in baseline licking (without prior water deprivation) for a 10% sucrose solution. We found that, compared to freezing, conditioned suppression of reward seeking was much more sensitive to fear conditioning and far less responsive to extinction training. As in previous work, we found that retrieval + extinction reduced post-extinction fear reinstatement when measured as freezing, but it did not reduce fear reinstatement when measured as conditioned suppression. This suggests that there is still residual fear following retrieval + extinction, or that this procedure only modifies memory traces in neural circuits relevant to the expression of freezing, but not to the suppression of reward seeking.
在啮齿动物的条件性恐惧研究中，冷冻已成为主要的测量方法，但对寻求奖励行为的条件性抑制可能提供一种与人类焦虑症更相关的测量方法；也就是说，一种衡量恐惧如何干扰愉悦活动享受的方法。先前的研究发现，在消退训练（回忆+消退）之前单独呈现恐惧条件刺激（CS）会导致恐惧更强烈、更持久地减少。本研究的目的是评估使用对寻求奖励的条件性抑制（通过减少10%蔗糖溶液的基线舔舐次数来操作化，且无先前的水剥夺）时，回忆+消退效应是否明显。我们发现，与冷冻相比，对寻求奖励的条件性抑制对恐惧条件作用更为敏感，而对消退训练的反应则小得多。与先前的研究一样，我们发现，以冷冻来衡量时，回忆+消退减少了消退后恐惧的恢复，但以条件性抑制来衡量时，它并没有减少恐惧的恢复。这表明在回忆+消退后仍存在残余恐惧，或者该程序仅改变了与冷冻表达相关的神经回路中的记忆痕迹，而没有改变与寻求奖励抑制相关的记忆痕迹。
