Investigating Spatial Memory Reconsolidation in Rats: Memory Updating, Effects of Aging, and Hippocampal Network Activity
Upon acquisition, memories undergo an initial stabilization, or consolidation, process after which they are generally resistant to interference. There is now an abundance of evidence that reactivation or retrieval of a consolidated memory opens up a window of time during which the memory can be strengthened, disrupted, or updated via a process of "reconsolidation". This dissertation is comprised of three experimental studies in rats aimed at investigating previously unexamined aspects of this dynamic memory process. The first study assessed whether spatial memories learned under positively-motivated conditions could be updated with new information following reactivation. Rats that learned a second spatial task in the same environmental context as a previously learned task intruded items from the second episode during recall of the first. This result suggests that the context reactivated the memory for the first task, triggering reconsolidation and updating of the memory. The second study used the memory updating effect obtained in the first study as a behavioral measure to investigate the effects of aging on reconsolidation. Unlike in the young rats, the context reminder did not lead to intrusions of the second learning episode during recall of the first. Older adult human participants in this study also showed a different pattern of results than what had been seen previously in young participants. Therefore, in humans as well as in rats, it appears that aging may lead to changes in spatial memory reconsolidation. The third study piloted an experiment to examine hippocampal network activity associated with the spatial memory reconsolidation task used in the first two studies. Preliminarily, we found that the context reminder manipulation was associated with more place field stability across some spatial tasks and that stability across certain tasks was positively related to our measure of memory updating. Additionally, we found evidence that the context reminder enhanced neural replay of some learning episodes. While preliminary, these results suggest that both place field stability and replay may play roles in this reconsolidation paradigm.
Hippocampus, Memory, Reconsolidation, Spatial Memory, Neuroscience, Aging
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