Department of Psychology, University of California, Riverside, California.
Department of Neurobiology & Behavior, University of California, Irvine, California.
Brain Behav. 2020 Mar;10(3):e01560. doi: 10.1002/brb3.1560. Epub 2020 Feb 3.
A fundamental component of episodic memory is the ability to differentiate new and highly similar events from previously encountered events. Numerous functional magnetic resonance imaging (fMRI) studies have identified hippocampal involvement in this type of mnemonic discrimination (MD), but few studies have assessed MD-related activity in regions beyond the hippocampus. Therefore, the current fMRI study examined whole-brain activity in healthy young adults during successful discrimination of the test phase of the Mnemonic Similarity Task.
In the study phase, participants made "indoor"/"outdoor" judgments to a series of objects. In the test phase, they made "old"/"new" judgments to a series of probe objects that were either repetitions from the memory set (targets), similar to objects in the memory set (lures), or novel. We assessed hippocampal and whole-brain activity consistent with MD using a step function to identify where activity to targets differed from activity to lures with varying degrees of similarity to targets (high, low), responding to them as if they were novel.
Results revealed that the hippocampus and occipital cortex exhibited differential activity to repeated stimuli relative to even highly similar stimuli, but only hippocampal activity predicted discrimination performance.
These findings are consistent with the notion that successful MD is supported by the hippocampus, with auxiliary processes supported by cortex (e.g., perceptual discrimination).
情景记忆的一个基本组成部分是区分新的和高度相似的事件与以前遇到的事件的能力。许多功能磁共振成像（fMRI）研究已经确定了海马体在这种记忆辨别（MD）中的作用，但很少有研究评估海马体以外区域的 MD 相关活动。因此，目前的 fMRI 研究在健康的年轻成年人中检查了整个大脑在记忆相似任务的测试阶段成功辨别时的活动。
在研究阶段，参与者对一系列物体进行“室内”/“室外”判断。在测试阶段，他们对一系列探测物体进行“旧”/“新”判断，这些探测物体要么是记忆集的重复（目标），要么与记忆集的物体相似（诱饵），要么是新的。我们使用阶跃函数评估与 MD 一致的海马体和全脑活动，以确定目标的活动与具有不同程度相似性的诱饵的活动（高、低）有何不同，将它们视为新的来回应。
结果表明，海马体和枕叶皮层对重复刺激的活动与即使是高度相似的刺激也存在差异，但只有海马体的活动预测了辨别表现。
这些发现与以下观点一致，即成功的 MD 由海马体支持，辅助过程由皮层支持（例如，感知辨别）。
