Abstract：
Fear attenuation is an etiologically relevant process for animal survival, since once acquired information needs to be continuously updated in the face of changing environmental contingencies. Thus, when situations are encountered that were originally perceived as fearful but are no longer so, fear must be attenuated, otherwise, it risks becoming maladaptive. But what happens to the original memory trace of fear during fear attenuation? In this chapter, we review the studies that have started to approach this question from an engram perspective. We find evidence pointing to both the original memory trace of fear being suppressed, as well as it being updated towards safety. These seemingly conflicting results reflect a well-established dichotomy in the field of fear memory attenuation, namely whether fear attenuation is mediated by an inhibitory mechanism that suppresses fear expression, called extinction, or by an updating mechanism that allows the fear memory to reconsolidate in a different form, called reconsolidation-updating. Which of these scenarios takes the upper hand is ultimately influenced by the behavioral paradigms used to induce fear attenuation, but is an important area for further study as the precise cell populations underlying fear attenuation and the molecular mechanisms therein can now be understood at unprecedented resolution.
摘要：
恐惧减弱是动物生存的病因学相关过程，因为一旦获得的信息需要在不断变化的环境突发事件中不断更新。因此，当遇到原本被认为是可怕但不再如此的情况时，恐惧必须减弱，否则,它有可能变得适应不良。但是在恐惧衰减期间，恐惧的原始记忆痕迹会发生什么？在本章中，我们回顾了已经开始从全字的角度来解决这个问题的研究。我们发现证据指向恐惧被压制的原始记忆痕迹，以及它被更新为安全。这些看似矛盾的结果反映了恐惧记忆衰减领域公认的二分法，即恐惧减弱是否由抑制恐惧表达的抑制机制介导，叫做灭绝，或者通过一种更新机制，让恐惧记忆以不同的形式重新巩固，称为重新合并更新。这些场景中哪一个占据上风最终会受到用于诱导恐惧衰减的行为范式的影响，但这是一个需要进一步研究的重要领域，因为现在可以以前所未有的分辨率理解恐惧衰减背后的精确细胞群及其分子机制。
