ABSTRACT

Theories of memory consolidation suggest the role of brain regions and connectivity between brain regions change as memories age. Human lesion studies indicate memories become hippocampus-independent over years, whereas animal studies suggest this process occurs across relatively short intervals, from days to weeks. Human neuroimaging studies suggest that changes in hippocampal and cortical activity and connectivity can be detected over these short intervals, but many of these studies examined only two time periods. We examined memory and fMRI activity for photos of indoor and outdoor scenes across four time periods to examine these neural changes more carefully. Participants (N = 21) studied scenes 1 hour, 1 day, 1 week, or 1 month before scanning. During scanning, participants viewed scenes, made old/new recognition memory judgments, and gave confidence ratings. Memory accuracy, confidence ratings, and response times changed with memory age. Brain activity in a widespread cortical network either increased or decreased with memory age, whereas hippocampal activity was not related to memory age. These findings were almost identical when effects of behavioral changes across time periods were minimized. Functional connectivity of the ventromedial prefrontal cortex with the posterior parietal cortex increased with memory age. By contrast, functional connectivity of the hippocampus with the parahippocampal cortex and fusiform gyrus decreased with memory age. In sum, we detected changes in cortical activity and changes in hippocampal and cortical connectivity with memory age across short intervals. These findings provide support for the predictions of systems consolidation and suggest that these changes begin soon after memories are formed.

摘要

记忆巩固理论表明，随着记忆的老化，大脑区域的作用以及大脑区域之间的连接会发生变化。人类损伤研究表明，记忆会随着时间的推移而变得独立于海马体，而动物研究表明，这一过程发生的时间间隔相对较短，从几天到几周不等。人类神经影像学研究表明，可以在这些较短的时间间隔内检测到海马和皮质活动和连接性的变化，但其中许多研究仅检查了两个时间段。我们检查了四个时间段内室内和室外场景照片的记忆和功能磁共振成像活动，以更仔细地检查这些神经变化。参与者 (N = 21) 在扫描前 1 小时、1 天、1 周或 1 个月研究场景。在扫描过程中，参与者查看场景，做出新旧识别记忆判断，并给出了信心评级。记忆准确性、置信度和响应时间随着记忆年龄的变化而变化。广泛的皮质网络中的大脑活动随着记忆年龄的增长而增加或减少，而海马活动与记忆年龄无关。当跨时间段的行为变化的影响最小化时，这些发现几乎是相同的。腹内侧前额叶皮质与后顶叶皮质的功能连接随着记忆年龄的增长而增强。相比之下，海马与海马旁皮质和梭状回的功能连接随着记忆年龄的增长而减弱。总之，我们检测到皮质活动的变化以及海马和皮质连接随着记忆年龄的变化而变化。