Nature:坏记忆或可以变美好
科技日报 · 2014/08/28
人的一生会经历很多人和事,难免会有一些难过的、恐惧的记忆。如果能改变这些坏的记忆当然是再好不过了。近日,发表在《自然》杂志上的一项研究发现,一项重写小鼠记忆的实验发现了涉及改变记忆的大脑回路,该项新成果给科学家提供了详细了解情感记忆如何能够被操纵的一种途径,同时,也提出了在大脑回路层面可以更改情感记忆的可能。


记忆可以改变吗?如果可以的话,这项技术或许在将来的某一天有望治愈那些正经受恐惧症、创伤后心理紊乱以及其他焦虑症困扰的患者们。日前,一项重写小鼠记忆的实验就发现了涉及改变记忆的大脑回路,8月28日出版的英国《自然》杂志对该相关神经科学的研究结果进行了报道。

回忆通常带有正面或者负面的情感联系,这种情感可能会随着时间变化,而记忆的其他细节,例如物理位置,却仍然准确。让情感和记忆发生关联的过程总体上不为人所知,虽然人们相信大脑的不同区域储存着一个记忆的不同组成部分。

此次,位于美国麻省的理化学研究所——麻省理工学院神经回路遗传研究中心科学家利根川进与他的研究团队,分析了小鼠杏仁核一部分中的细胞以及海马体的齿状回一部分中的细胞,二者是如何在记忆形成时被激活的。其中,杏仁核被认为是负责编码正面或者负面感受的部位,而海马体则被认为编码语境信息的部位。

实验中,雄性小鼠被训练成把一个蓝光信号和恐惧的记忆建立联系(恐惧的记忆通过受到一次小型电击建立),或者和一个愉悦的记忆建立联系(愉悦的记忆通过和一只雌性小鼠互动建立),导致这些动物或躲避或偏好一个特定的位置。接下来,为了让和这个位置相关的正面或负面记忆交换,小鼠接受了相反的训练。

以此研究人员发现,海马体齿状回的神经回路在试图扭转记忆时会被激活,导致海马体齿状回和杏仁核之间的记忆痕迹的连接会出现改变。这些研究表明,海马体齿状回情感记忆的痕迹,可以在有新的和语境相关的信息或位置出现时重写,从而形成新的情感基因。

该项新成果给科学家提供了详细了解情感记忆如何能够被操纵的一种途径,同时,也提出了在大脑回路层面可以更改情感记忆的可能。

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  • Bidirectional switch of the valence associated with a hippocampal contextual memory engram

    The valence of memories is malleable because of their intrinsic reconstructive property1. This property of memory has been used clinically to treat maladaptive behaviours2. However, the neuronal mechanisms and brain circuits that enable the switching of the valence of memories remain largely unknown. Here we investigated these mechanisms by applying the recently developed memory engram cell- manipulation technique3, 4. We labelled with channelrhodopsin-2 (ChR2) a population of cells in either the dorsal dentate gyrus (DG) of the hippocampus or the basolateral complex of the amygdala (BLA) that were specifically activated during contextual fear or reward conditioning. Both groups of fear-conditioned mice displayed aversive light-dependent responses in an optogenetic place avoidance test, whereas both DG- and BLA-labelled mice that underwent reward conditioning exhibited an appetitive response in an optogenetic place preference test. Next, in an attempt to reverse the valence of memory within a subject, mice whose DG or BLA engram had initially been labelled by contextual fear or reward conditioning were subjected to a second conditioning of the opposite valence while their original DG or BLA engram was reactivated by blue light. Subsequent optogenetic place avoidance and preference tests revealed that although the DG-engram group displayed a response indicating a switch of the memory valence, the BLA-engram group did not. This switch was also evident at the cellular level by a change in functional connectivity between DG engram-bearing cells and BLA engram-bearing cells. Thus, we found that in the DG, the neurons carrying the memory engram of a given neutral context have plasticity such that the valence of a conditioned response evoked by their reactivation can be reversed by re-associating this contextual memory engram with a new unconditioned stimulus of an opposite valence. Our present work provides new insight into the functional neural circuits underlying the malleability of emotional memory.

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