Evidence for an evolutionary conserved memory coding scheme in the mammalian hippocampus

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Thome, Alexander
Marrone, Diano F.
Ellmore, Timothy M.
Chawla, Monica K.
Lipa, Peter
Ramirez-Amaya, Victor
Lisanby, Sarah H.
McNaughton, Bruce L.
Barnes, Carol A.
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Society for Neuroscience
Decades of research identify the hippocampal formation as central to memory storage and recall. Events are stored via distributed population codes, the parameters of which (e.g., sparsity and overlap) determine both storage capacity and fidelity. However, it remains unclear whether the parameters governing information storage are similar between species. Because episodic memories are rooted in the space in which they are experienced, the hippocampal response to navigation is often used as a proxy to study memory. Critically, recent studies in rodents that mimic the conditions typical of navigation studies in humans and non human primates (i.e.,virtual reality) show that reduced sensory input alters hippocampal representations of space. The goal of this study was to quantify this effect and determine whether there are commonalities in information storage across species. Using functional molecular imaging, we observe that navigation in virtual environments elicits activity in fewer CA1 neurons relative to real-world conditions. Conversely, comparable neuronal activity is observed in hippocampus region CA3 and the dentate gyrus under both conditions. Surprisingly, we also find evidence that the absolute number of neurons used to represent an experience is relatively stable between non human primates and rodents. We propose that this convergence reflects an optimal ensemble size for episodic memories.
Sherpa Romeo yellow journal. Open access article. Creative Commons Attribution 4.0 International License (CC BY 4.0) applies
Neural coding , Neuroethology , Primate , Rodent , Spatial cognition , Virtual reality , CA3 , CA1
Thome, A., Marrone, D. F., Ellmore, T. M., Chawla, M. K., Lipa, P., Ramirez-Amaya, V.,...Barnes, C. A. (2017). Evidence for an evolutionary conserved memory coding scheme in the mammalian hippocampus. Journal of Neuroscience, 37(10), 2795-2801. DOI:10.1523/JNEUROSCI.3057-16.2017