Packard Pau Alexander, Rodríguez-Fornells Antoni, Stein Lilian Milnitsky, Nicolás Berta, Fuentemilla Lluís
Cognition and Brain Plasticity Group, Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain; Department of Basic Psychology, University of Barcelona, Barcelona, Spain.
Cognition and Brain Plasticity Group, Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain; Department of Basic Psychology, University of Barcelona, Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.
Neurobiol Learn Mem. 2014 Dec;116:96-104. doi: 10.1016/j.nlm.2014.09.004. Epub 2014 Sep 26.
Recent accounts of Posttraumatic Stress Disorder (PTSD) suggest that the encoding of an episode within a fearful context generates different implicit and explicit memory representations. Whilst implicit memory traces include the associated emotional states, explicit traces include a recoding into an abstract or gist-based structural context of the episode. Theoretically, the long-term preservation of implicit memory traces may facilitate the often untreatable memory intrusions in PTSD. Here, we tracked in two experiments how implicit and explicit memory traces for fearful episodes dissociate and evolve over time. Subjects (N=86) were presented with semantically-related word-lists in a contextual fear paradigm and tested for explicit memories either immediately (i.e., 30 min) or after a delay (i.e., 1 or 2 weeks) with a verbal recognition task. Skin Conductance Response (SCR) was used to assess implicit memory responses. Subjects showed high memory accuracy for words when tested immediately after encoding. At test, SCR was higher during the presentation of verbatim but not gist-based words encoded in a fearful context, and remained unchanged after 2 weeks, despite subjects being unaware of words' encoding context. We found no clear evidence of accurate explicit memory traces for the fearful or neutral contexts of words presented during encoding, either 30 min or 2 weeks afterwards. These findings indicate that the implicit, but not the explicit, memory trace of a fearful context of an episode can be detected at long-term through SCR and is dissociated from the gist-based memory. They may have implicationstowards the understanding of how the processing of fearful memoriescould lead to PTSD.
近期关于创伤后应激障碍（PTSD）的研究表明，在恐惧情境中对某一事件进行编码会产生不同的内隐记忆和外显记忆表征。内隐记忆痕迹包含相关的情绪状态，而外显记忆痕迹则包括将事件重新编码为基于抽象或主旨的结构背景。从理论上讲，内隐记忆痕迹的长期保存可能会促使PTSD中常常难以治疗的记忆侵扰。在此，我们通过两个实验追踪了恐惧事件的内隐记忆和外显记忆痕迹如何随着时间的推移而分离和演变。研究对象（N = 86）在情境恐惧范式中被呈现语义相关的单词列表，并通过言语识别任务在编码后立即（即30分钟）或延迟（即1或2周）后测试外显记忆。皮肤电传导反应（SCR）用于评估内隐记忆反应。在编码后立即测试时，研究对象对单词表现出较高的记忆准确性。在测试中，对于在恐惧情境中编码的逐字表述而非基于主旨的单词，呈现过程中SCR更高，并且在2周后保持不变，尽管研究对象并未意识到单词的编码背景。在编码后30分钟或2周时，我们均未发现有明确证据表明对编码过程中呈现的单词的恐惧或中性情境存在准确的外显记忆痕迹。这些发现表明，通过SCR可以长期检测到事件恐惧情境的内隐记忆痕迹，而非外显记忆痕迹，并与基于主旨的记忆相分离。它们对于理解恐惧记忆的处理如何导致PTSD可能具有启示意义。
