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Bridging Scales in Episodic Memory Research: From Comparative Neuroanatomy to Cognitive Theory

Chairs: Daniel Reznik^1,2, Charan Ranganath³; ¹Kavli Institute for Systems Neuroscience (NTNU), ²University of Oxford, ³UC Davis
Presenters: Daniel Reznik, Dorothy Tse, Nora Newcombe, Charan Ranganath

Recent years have provided important breakthroughs in episodic memory research, originating in traditionally disconnected fields of inquiry. Integrating these bleeding-edge discoveries and novel insights into the cognitive theory of human episodic memory has been a historically challenging task due to limited cross-field exchanges, resulting in parallel rather than integrated research lineages. The goal of the current symposium is twofold. First, we would like to showcase recent empirical and theoretical advances in evolutionary, developmental and aging neuroscience that are projected to shape and inspire research into the neural and cognitive mechanisms of episodic memory in coming years. Second, by bringing together speakers representing complementary levels of analysis, methods and expertise, we would like to highlight the critical need for an integrative approach to facilitate deeper insights into the architecture of human episodic memory, connecting evolution, development and cognitive theory. In the first talk, Daniel Reznik will present the recently discovered organization of the human entorhinal-hippocampal system serving as an anatomical blueprint supporting episodic memory in the mammalian lineage. Next, Dorothy Tse will present recent insights from cross-species approaches to studying episodic and spatial memory across the lifespan. Nora Newcombe will then overview evidence concerning the developmental trajectory of episodic memory subdomains in children. Finally, Charan Ranganath will integrate these different scales and levels of analysis into a broader theory of episodic memory that emphasizes cortico-hippocampal network dynamics. A discussion between the speakers and the audience will conclude the symposium, identifying future research directions and the cross-field collaborations needed to pursue them.

Presentations

Cross-species anatomical blueprints for episodic memory and beyond

Daniel Reznik^1,2; ¹Kavli Institute for Systems Neuroscience (NTNU), ²University of Oxford

Animal tract-tracing studies provided critical insights into the organizational principles of the hippocampal system in multiple species, thus defining the anatomical boundaries within which animal mnemonic functions operate. However, no clear framework defining the anatomical organization of the human hippocampal system exists. This gap in knowledge originates in notoriously low fMRI data quality in the human medial temporal lobe and in group-level blurring of idiosyncratic and fine-grained anatomy of small and physically adjacent brain structures comprising the hippocampal system. In this talk, I will present recent 7 Tesla fMRI data, which overcame these longstanding challenges and allowed to explore in detail the whole-brain circuitry associated with subregions of the human medial temporal lobe, and to examine the intrinsic organization of entorhinal-hippocampal circuits with unprecedented anatomical precision at the individual-subject level. This approach revealed a previously unknown organizational principle of the human hippocampal system that is found in all studied mammalian species. These findings facilitate the study of the developmental and evolutionary trajectory of hippocampal-cortical interactions, and prompt a reformulation of the neuroanatomical basis of episodic memory and its subdomains.

How prior knowledge shapes episodic memory across the lifespan

Dorothy Tse¹; ¹Edge Hill University

Prior knowledge can shape how new information is learned, integrated and retained. Organised knowledge structures, or schemas, allow new experiences to be related to and integrated with what is already known. Previous studies in rodents have demonstrated that prior knowledge can accelerate learning and promote the rapid consolidation of new episodic-like information, providing an important framework for understanding how existing knowledge influences new memory formation. Building on these findings, this talk will present recent human studies examining how prior knowledge shapes episodic and spatial memory. Using comparable behavioural paradigms and virtual spatial environments, these studies investigate how established knowledge structures influence the learning and retention of new associations across the lifespan. In particular, the work examines what happens when younger and older adults learn new information that is either consistent or inconsistent with an existing schema. Recent findings suggest that schema consistency can support memory in both age groups, but that its benefits may be especially pronounced in older adults when acquiring new information. By contrast, schema-inconsistent information places greater demands on learning because it cannot be readily incorporated into an established knowledge structure. These findings provide insight into how prior knowledge can support the formation of new episodic memories and how this relationship changes across the lifespan. They also highlight the importance of considering not only whether prior knowledge is available, but whether new information is consistent or inconsistent with what is already known.

Understanding the development of episodic memory

Nora Newcombe¹; ¹Temple University

Humans (and many other mammals) typically do not remember specific events from the first part of their lives, which seems odd because they do acquire many skills and habits. This talk will outline a varying-timetables view of the developmental trajectory of episodic memory in which what-where-when memories are rudimentary in infancy, and develop later than implicit and semantic memory. Furthermore, episodic memory is itself componential, with varying timetables and determinants for the different strands, such as relational binding, pattern separation, holistic completion, and true event memory. By contrast, in the early-competence view, episodic memory is present in infancy but masked or rendered inaccessible by factors such as lack of verbal skills or immature neural substrates. The talk will review the evidence and identify key unanswered questions, notably how we define episodic memory, how we grade it from rudimentary to robust, what criteria we use to characterize behavioral tasks, and how we compare ages when tasks necessarily vary.

Episodic memory: A tale of two modes

Charan Ranganath¹; ¹UC Davis

The capacity to re-experience a moment from the past, known as episodic memory, allows us to navigate the present and plan for the future. Tulving defined episodic memory in 1972, and yet, with almost 150 years of research under our belts, it still remains controversial and enigmatic. On one hand, episodic memories seem to be based on traces of experience, carrying objective information about specific moments in time, and on the other, they are imaginative reconstructions, built on a scaffold of prior knowledge. The tension between these perspectives can be reconciled by conceptualizing episodic memory not as a readout from a static memory system, but as the outcome of two neurocognitive modes— a generative mode that facilitates schema-based inference and prediction, and a contextual mode that binds memories to context-specific anchor points. Drawing from experimental findings and computational models, I will describe how these modes arise from dynamic cortico-hippocampal interactions, allowing episodic memory to be at once precise and constructive.