A symposium on medial temporal lobe functions beyond the hippocampus will be featured in the upcoming Park City Winter Neurobiology of Learning and Memory Meeting. Some of the talks will focus on these regions’ involvement in domain-specific pattern separation.

Beyond the Hippocampus: Medial Temporal Cortices’ Mnemnonic Functions and Vulnerability to Age-related Decline

Chair: Michael Yassa, PhD

Johns Hopkins University
Date & Time: January 3-4, 2014 (tentative)

There has been a growing interest in the mnemonic functions of the medial temporal cortices outside of the hippocampus. While it is clear that the perirhinal, entorhinal and parahippocampal/postrhinal cortices play critical roles in service of long-term memory, the exact computational functions of these regions remain to be elucidated. Electrophysiological recordings in the two subdivisions of the entorhinal cortex, for example, have shown strong spatial coding signals (i.e. grid cells) in the medial portion (MEC) but not the lateral portion (LEC). More recent work has suggested that LEC neurons may be coding for objects or rather the “world out there” which, together with spatial signals in MEC could provide input to drive hippocampal computations. This division of labor extends to the perirhinal (PRC) and parahippocampal/postrhinal (PHC/POR) cortices where PRC has demonstrated sensitivity to input changes in the object domain whereas PHC/POR has demonstrated sensitivity to input changes in the spatial or contextual domain. Furthermore, studies in aged rats have strongly suggested that the PRC-LEC pathway but not the POR-MEC pathway may be selectively vulnerable to age-related cognitive decline. Behavioral and neuroimaging studies in humans have also supported similar conclusions. The goals of this session are: (1) shed some light on the different computations in PRC-LEC and PHC-MEC and how they come together to provide object-in-context input for hippocampal processing, and (2) discuss recent cross-species data on how some but not all of these extrahippocampal regions change with age and whether these changes are predictive of cognitive decline. The speakers for this symposium are:

Michael A. Yassa, Johns Hopkins University (Chair)
Discussion of LEC/MEC and PRC/PHC high-resolution neuroimaging data in humans and distinguishing object vs. spatial pattern separation in these regions as well as selective vulnerability of PRC-LEC pathway to aging in humans.

Sara Burke, University of Arizona
Discussion of PRC signals in older rats and relationship to object pattern separation and object processing deficits.

Jim Knierim, Johns Hopkins University
Discussion of MEC/LEC signals in rats, and a selective role of LEC in nonspatial processing of contextual cues and relationship to hippocampal processing.

Michela Gallagher, Johns Hopkins University
Discussion of LEC vulnerability to the aging process from a molecular perspective in an outbred model of aged rats and relationship to memory performance.

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