Phylogeny of the anatomical projections from the neocortex to the hippocampal region: evolutionary insights into the nature of declarative memory

Poster Session E - Monday, April 15, 2024, 2:30 – 4:30 pm EDT, Sheraton Hall ABC

Daniel Reznik¹ (reznik@cbs.mpg.de), Piotr Majka², Marcello Rosa³, Menno P Witter⁴, Christian F Doeller^1,5,6; ¹Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ²Nencki Institute of Experimental Biology of the Polish Academy of Sciences, Warsaw, Poland, ³Department of Physiology and Neuroscience Program, Biomedicine Discovery Institute, Monash University, Australia, ⁴Kavli Institute for Systems Neuroscience, NTNU Norwegian University of Science and Technology, Trondheim, Norway, ⁵Wilhelm Wundt Institute of Psychology, Leipzig University, Leipzig, Germany, ⁶Department of Psychology, Technische Universität Dresden, Dresden, Germany

Unlike the mammalian neocortex, the hippocampal region largely preserved its cytoarchitectural organization and its role in mnemonic functions throughout more than 200 million years of mammalian evolution. Following recent advances in imaging of the human hippocampal region (Reznik et al., 2023), in the current study we sought to leverage this contrast and to examine changes in anatomical connectivity between the hippocampal region and the broader cortex across species. Specifically, we examined differences in unimodal and transmodal cortical input to the perirhinal cortex, entorhinal cortex, and the parahippocampal cortex (postrhinal cortex in the rodent) in the rat, marmoset, macaque, and human. Our results demonstrate that mammalian evolution, culminating in humans, has been associated with a decrease in unimodal input and a corresponding increase in transmodal input to the hippocampal region. Importantly, these changes in connectivity cannot be explained merely by changes in the relative size of transmodal areas across species. Furthermore, we found that in the primate lineage, cortical input from the broader cortex to the entorhinal cortex was dominated by transmodal areas compared with the cortical input to the perirhinal/parahippocampal cortices. Our observations provide a comparative anatomical framework supporting the fundamentally constructive nature of declarative memory and indicate that memory-related processes in different species operate on different types of sensory information.

Topic Area: LONG-TERM MEMORY: Other