Department of Psychology, Humboldt University of Berlin, Berlin 10117, Germany
Department of Psychology, Humboldt University of Berlin, Berlin 10117, Germany.
J Neurosci. 2023 Nov 1;43(44):7337-7350. doi: 10.1523/JNEUROSCI.2265-22.2023. Epub 2023 Sep 6.
Although episodic memory and visual processing decline substantially with healthy aging, semantic knowledge is generally spared. There is evidence that older adults' spared semantic knowledge can support episodic memory. Here, we used functional magnetic resonance imaging (fMRI) combined with representational similarity analyses (RSAs) to examine how novel visual and preexisting semantic representations at encoding predict subjective memory vividness at retrieval. Eighteen young and seventeen older adults (female and male participants) encoded images of objects during fMRI scanning and recalled these images while rating the vividness of their memories. After scanning, participants discriminated between studied images and similar lures. RSA based on a deep convolutional neural network and normative concept feature data were used to link patterns of neural activity during encoding to visual and semantic representations. Relative to young adults, the specificity of activation patterns for visual features was reduced in older adults, consistent with dedifferentiation. However, the specificity of activation patterns for semantic features was enhanced in older adults, consistent with hyperdifferentiation. Despite dedifferentiation, visual representations in early visual cortex (EVC) predicted high memory vividness in both age groups. In contrast, semantic representations in lingual gyrus (LG) and fusiform gyrus (FG) were associated with high memory vividness only in the older adults. Intriguingly, data suggests that older adults with lower specificity of visual representations in combination with higher specificity of semantic representations tended to rate their memories as more vivid. Our findings suggest that memory vividness in aging relies more on semantic representations over anterior regions, potentially compensating for age-related dedifferentiation of visual information in posterior regions. Normal aging is associated with impaired memory for events while semantic knowledge might even improve. We investigated the effects of aging on the specificity of visual and semantic information in the brain when viewing common objects and how this information enables subsequent memory vividness for these objects. Using functional magnetic resonance imaging (fMRI) combined with modeling of the stimuli we found that visual information was represented with less specificity in older than young adults while still supporting memory vividness. In contrast semantic information supported memory vividness only in older adults and especially in those individuals that had the lowest specificity of visual information. These findings provide evidence for a spared semantic memory system increasingly recruited to compensate for degraded visual representations in older age.
尽管情节记忆和视觉处理在健康老化过程中会大幅下降，但语义知识通常不会受到影响。有证据表明，老年人未受影响的语义知识可以支持情节记忆。在这里，我们使用功能磁共振成像 (fMRI) 结合表示相似性分析 (RSA) 来研究在编码时新的视觉和预先存在的语义表示如何预测检索时的主观记忆生动度。18 名年轻成年人和 17 名老年人（男女参与者）在 fMRI 扫描期间对物体图像进行编码，并在回忆这些图像时对记忆的生动度进行评分。扫描后，参与者对学习过的图像和相似的诱饵进行了区分。基于深度卷积神经网络和规范概念特征数据的 RSA 用于将编码期间的神经活动模式与视觉和语义表示联系起来。与年轻成年人相比，老年人的视觉特征激活模式特异性降低，这与去分化一致。然而，老年人的语义特征激活模式特异性增强，与超分化一致。尽管去分化，早期视觉皮层 (EVC) 的视觉表示仍然可以预测两个年龄组的高记忆生动度。相比之下，LG 和 FG 中的语义表示仅与老年人的高记忆生动度相关。有趣的是，数据表明，视觉表示特异性较低且语义表示特异性较高的老年人倾向于认为他们的记忆更生动。我们的研究结果表明，老化过程中的记忆生动度更多地依赖于语义表示，而不是前脑区域，可能补偿了后脑区域中与年龄相关的视觉信息去分化。正常老化与事件记忆受损有关，而语义知识甚至可能改善。我们研究了在观看常见物体时大脑中视觉和语义信息的特异性随年龄的变化以及这些信息如何使这些物体的后续记忆生动度。使用 fMRI 结合对刺激的建模，我们发现老年人的视觉信息表示特异性低于年轻人，而仍然支持记忆生动度。相比之下，语义信息仅在老年人中支持记忆生动度，尤其是在视觉信息特异性最低的个体中。这些发现为一个未受影响的语义记忆系统提供了证据，该系统在老年时越来越多地被招募来补偿视觉表示的退化。
