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Temporal coding mediates spatial computation in the brain
Colin Molter
Riken Brain Science Institute
Laboratory for Dynamics of Emergent Intelligence
cmolter@brain.riken.jp

Abstract

We know that the hippocampus facilitates memory formation and spatial representation and that hippocampal place cells establish spatial representations, with firing activity modulated by theta oscillation of local field potential in term of `theta phase precession'. In addition, it has been recently reported that medial entorhinal cortical (MEC) cells, which mediates the majority of the cortical input to the hippocampus, fire with theta phase precession when the rat is located at any of the vertices of a regular grid of equilateral triangles covering the environment. Clarifying how spatial and temporal activities in the hippocampus interact to form and recall memories and process information, is essential for a more coherent understanding of the way the hippocampus works. Here, we show that entorhinal theta phase precession is crucial for the transformation of entorhinal grid fields to hippocampal place field represen- tations, and that hippocampal phase precession emerges associated with this process. Our computational model quantitatively shows the emergence of place fields and phase precession, and demonstrates a causal relationship between spike timing and spatial representations. Together, these findings suggest, for the first time, that brains use temporal coding for space computation in the entorhinal-hippocampal system. This appears also as one of the first concrete example for the importance of temporal coding in the brain.

Keywords

Hyppocampus, Dynamical System, Neural Network, Memory