Liang Jackson C, Preston Alison R
Department of Psychology, University of Toronto, Toronto, Canada.
Department of Psychology, Austin, TX, USA; Department of Neuroscience, Austin, TX, USA; Center for Learning & Memory, University of Texas at Austin, Austin, TX, USA.
Cortex. 2017 Jun;91:67-78. doi: 10.1016/j.cortex.2016.09.011. Epub 2016 Oct 12.
Leading theories propose that when remembering past events, medial temporal lobe (MTL) structures reinstate the neural patterns that were active when those events were initially encoded. Accurate reinstatement is hypothesized to support detailed recollection of memories, including their source. While several studies have linked cortical reinstatement to successful retrieval, indexing reinstatement within the MTL network and its relationship to memory performance has proved challenging. Here, we addressed this gap in knowledge by having participants perform an incidental encoding task, during which they visualized people, places, and objects in response to adjective cues. During a surprise memory test, participants saw studied and novel adjectives and indicated the imagery task they performed for each adjective. A multivariate pattern classifier was trained to discriminate the imagery tasks based on functional magnetic resonance imaging (fMRI) responses from hippocampus and MTL cortex at encoding. The classifier was then tested on MTL patterns during the source memory task. We found that MTL encoding patterns were reinstated during successful source retrieval. Moreover, when participants made source misattributions, errors were predicted by reinstatement of incorrect source content in MTL cortex. We further observed a gradient of content-specific reinstatement along the anterior-posterior axis of hippocampus and MTL cortex. Within anterior hippocampus, we found that reinstatement of person content was related to source memory accuracy, whereas reinstatement of place information across the entire hippocampal axis predicted correct source judgments. Content-specific reinstatement was also graded across MTL cortex, with PRc patterns evincing reactivation of people and more posterior regions, including PHc, showing evidence for reinstatement of places and objects. Collectively, these findings provide key evidence that source recollection relies on reinstatement of past experience within the MTL network.
主流理论认为，在回忆过去的事件时，内侧颞叶（MTL）结构会恢复这些事件最初编码时活跃的神经模式。据推测，准确的恢复有助于对记忆进行详细回忆，包括其来源。虽然多项研究已将皮层恢复与成功检索联系起来，但在MTL网络中对恢复进行索引及其与记忆表现的关系已被证明具有挑战性。在这里，我们通过让参与者执行一项附带编码任务来填补这一知识空白，在此过程中，他们根据形容词提示想象人物、地点和物体。在一次意外的记忆测试中，参与者看到学习过的和新的形容词，并指出他们为每个形容词执行的想象任务。训练了一个多变量模式分类器，以根据编码时海马体和MTL皮层的功能磁共振成像（fMRI）反应来区分想象任务。然后在源记忆任务期间对MTL模式进行测试。我们发现，在成功的源检索过程中，MTL编码模式会恢复。此外，当参与者做出源错误归因时，MTL皮层中错误源内容的恢复可以预测错误。我们还观察到沿海马体和MTL皮层前后轴的特定内容恢复梯度。在海马体前部，我们发现人物内容的恢复与源记忆准确性有关，而整个海马体轴上地点信息的恢复则预测了正确的源判断。特定内容的恢复在MTL皮层中也呈梯度分布，PRc模式显示人物的重新激活，而包括PHc在内的更靠后的区域则显示地点和物体恢复的证据。总的来说，这些发现提供了关键证据，表明源回忆依赖于MTL网络中过去经验的恢复。
