Dartmouth Events

Please join us for a colloquium in Moore BO3 on Thursday, April 17, 2025, starting at 1:05 p.m., given by Mark Sheffield, Associate Professor, Department of Neurobiology and Institute for Neuroscience, at The University of Chicago.

Title:  The Neural Dynamics of Memory Formation in the Hippocampus

Abstract:  Memory formation in the hippocampus is a complex process shaped by multiple, often independently studied mechanisms, which need to be integrated into a cohesive framework. Our current conceptual model proposes that memory formation is dynamically regulated by novelty-driven modulation of CA1 activity. We hypothesize that novelty detection by the locus coeruleus (LC) triggers a transient memory formation state in CA1, which lowers dendritic inhibition of CA1 pyramidal cells. This reduction in inhibition facilitates increased dendritic spike prevalence and behavioral timescale synaptic plasticity (BTSP) events, both of which enhance synaptic potentiation and contribute to the rapid formation of place fields (PFs), predominantly driven by CA3 inputs. At the population level, this leads to a progressive refinement of the spatial code, resulting in improved spatial accuracy. We propose that right CA3 inputs play a dominant role during this learning period due to elevated activity, which is crucial for developing reliable and high-gain CA1 place fields. Furthermore, we speculate that BTSP events continue to shape CA1 PFs after their initial formation, gradually shifting them earlier in time (backwards in space), making them increasingly predictive as animals learn about their environment. Once familiarity with the environment is established, we suggest that the system partially stabilizes, while continuing to update and drift, reflecting ongoing plasticity and continuous learning. This conceptual framework aims to integrate disparate observations into a unified model, clarifying how novelty detection, dendritic modulation, synaptic plasticity, and lateralized CA3 input dynamics collectively shape the formation, refinement, and maintenance of hippocampal spatial representations during learning.

Coffee, tea, and cider donuts will be available a few minutes before and after the talk in the foyer space outside of Moore .