Positive and negative impacts of prior knowledge on episodic memory consolidation - PROJECT SUMMARY The study of how prior knowledge shapes new experiences is central to the science of memory and its role in pathology, but there is a critical lack of understanding of how prior knowledge shapes the long-term storage and transformation of a new memory. Current explanations of how episodic memories change over time put forward the hypothesis that neural traces in the hippocampus become distributed across cortical regions (systems-level consolidation), a process that unfolds over extended timescales through persisting neural dynamics that unfold after learning. Emerging evidence conflicts with this, suggesting that prior knowledge can speed or even bypass this process, such that increased cortical dynamics during and after learning results in the immediate generation of a cortical memory representation that supports a stabilized memory (rapid consolidation). However, current research focuses mainly on the impact of prior knowledge on memory accessibility, rather than characterizing the quality of the enduring memory and its assimilation with other information, leaving open questions about how prior knowledge governs the transformation of new memories and their integration into pre-existing cortical networks. This application describes a 5-year plan to investigate how prior knowledge can enhance or distort new memories, focusing on ways that prior knowledge shapes learning and consolidation of new events. The plan consists of functional neuroimaging (fMRI) and non-invasive brain stimulation techniques (TMS), applied to both well-validated and novel experimental approaches and targeting healthy human adults. The central hypothesis is that, if prior knowledge is activated during new learning, memory for new items undergoes rapid consolidation, regardless of if the encoded event is congruent with or conflicts with the activated knowledge. Specifically, the activation prior knowledge during learning will increase cortical involvement during learning and elevate cortical based neural dynamics in periods of awake rest after learning, relative to more hippocampal based processing predicted by classic systems consolidation models. Critically, the rapidly consolidated memories would be both more durable and more easily integrated with prior knowledge than if they were unrelated to prior knowledge. Aim 1 will test these hypotheses with the prediction that new memories that are congruent with prior knowledge will become more integrated with each other, using a novel test of behavioral integration. Aim 2 will test parallel hypotheses when new experiences conflict with prior knowledge, using a well- validated experimental design. Critically, the prediction is that the same rapid consolidation processes would give rise faster and greater distortions in these memories. Completion of these aims will reveal novel insights into how prior knowledge impacts the trajectory of new memories and will shed light on how dysfunction in this process leads to pathology. This has the potential to aid clinical researchers in the development of treatments for patients suffering from subtle impairments in memory, such as stroke patients.
