Kim Jee Hyun, Richardson Rick
School of Psychology, The University of New South Wales, Sydney 2052, Australia.
Neurobiol Learn Mem. 2007 Jul;88(1):48-57. doi: 10.1016/j.nlm.2007.03.004. Epub 2007 Apr 24.
Recently, studies from our laboratory have shown that 16-day-old rats, in contrast to 23-day-old rats, fail to show either ABA renewal or recovery of an extinguished fear response following a pre-test injection of FG7142 [Kim, J. H. & Richardson, R. (2007). A developmental dissociation of context and GABA effects on extinguished fear in rats. Behavioral Neuroscience; Yap & Richardson, unpublished data]. The present study, using freezing as a measure of learned fear, extends these findings by examining whether there is a developmental difference in susceptibility to reinstatement following extinction. 16- and 23-day-old rats were trained to fear a white-noise conditioned stimulus (CS) by pairing it with a shock unconditioned stimulus (US). This fear was subsequently extinguished by non-reinforced presentations of the CS. Some rats received a post-extinction Reminder which consisted of a single presentation of a reduced-intensity US. Experiments 1 and 2 demonstrated that this Reminder was effective in reinstating extinguished fear in 23-day-olds, and that this reinstatement effect was context-specific in rats this age. In contrast, 16-day-old rats failed to show the reinstatement effect in either experiment. The failure to observe a post-extinction reinstatement effect in the 16-day-olds was not due to a general ineffectiveness of the Reminder treatment at this age because it did alleviate spontaneous forgetting in rats this age (Experiment 3). Taken together, the results suggest that fundamentally different processes may mediate extinction early in development compared to later in development.
最近，我们实验室的研究表明，与23日龄的大鼠相比，16日龄的大鼠在预测试注射FG7142后，既未表现出ABA恢复，也未表现出消退恐惧反应的恢复[Kim, J. H. & Richardson, R. (2007). 大鼠中情境和GABA对消退恐惧的影响的发育解离。行为神经科学；Yap和Richardson，未发表数据]。本研究以僵住作为习得恐惧的衡量指标，通过检查消退后恢复的易感性是否存在发育差异来扩展这些发现。对16日龄和23日龄的大鼠进行训练，使其通过将白噪声条件刺激（CS）与电击非条件刺激（US）配对来恐惧该CS。随后通过CS的非强化呈现使这种恐惧消退。一些大鼠在消退后接受了一次提醒，该提醒包括一次强度降低的US呈现。实验1和2表明，这种提醒在恢复23日龄大鼠消退的恐惧方面是有效的，并且这种恢复效应在这个年龄段的大鼠中是情境特异性的。相比之下，16日龄的大鼠在两个实验中均未表现出恢复效应。16日龄大鼠未观察到消退后恢复效应并非由于该年龄段提醒处理普遍无效，因为它确实减轻了这个年龄段大鼠的自发遗忘（实验3）。综上所述，结果表明，与发育后期相比，发育早期消退可能由根本不同的过程介导。
