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bioRxiv · 10.1101/340414

\"Small and many\" is the strategy for robust and efficient information transfer in dendritic spines

Tottori, T. S.·Fujii, M.·Kuroda, S.
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Abstract

A dendritic spine is a small structure on the dendrites of a neuron that processes input timing information from other neurons. Tens of thousands of spines are present on a neuron. Why are spines so small and many? Because of the small number of molecules in the spine volume, biochemical reactions become stochastic. Therefore, we used the stochastic simulation model of N-methyl-D-aspartate receptor (NMDAR)-mediated Ca2+ increase to address this issue. NMDAR-mediated Ca2+ increase codes the input timing information between prespiking and postspiking. We examined how much the input timing information is encoded by Ca2+ increase against prespiking fluctuation. We found that the input timing information encoded in the spine volume (10-1 m3) is more robust against prespiking fluctuation than that in the cell volume (103 m3). We further examined the mechanism of the robust information transfer in the spine volume. We demonstrated that the necessary and sufficient condition for robustness is that the stochastic NMDAR-mediated Ca2+ increase (intrinsic noise) becomes much larger than the prespiking fluctuation (extrinsic noise). The condition is satisfied in the spine volume, but not in the cell volume. Moreover, we compared the information transfer in many small \"spine-volume\" spines with that in a single large \"cell-volume\" spine. We found that many small \"spine-volume\" spines is much more efficient for information transfer than a single large \"cell-volume\" spine when prespiking fluctuation is large. Thus, robustness and efficiency are two functional reasons why dendritic spines are so small and many.\n\nSignificanceA dendritic spine is a small platform for information processing in a neuron, and tens of thousands of spines are present on a neuron. Why are spines so small and many? Here we addressed this issue using stochastic simulation of NMDAR-mediated Ca2+ increase in a spine. We demonstrated that smallness of a spine enables the robust information transfer against input fluctuation, and that many small spines are much efficient for information transfer than a single large cell. This is the first demonstration that shows the advantage of the \"small and many\" of spines in information processing. The \"small and many\" strategy may be used not only in spines of a neuron, but also in other small and many intracellular organelles.

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Tottori, T. S., Fujii, M., Kuroda, S.. 2018-06-06. \"Small and many\" is the strategy for robust and efficient information transfer in dendritic spines. https://doi.org/10.1101/340414

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