A geometric attractor mechanism for self-organization of entorhinal grid modules

TL;DR

This paper proposes a dynamical self-organization mechanism for the modular structure of grid cells in the entorhinal cortex, explaining their discrete scales and ratios through geometric and inhibitory interactions.

Contribution

It introduces a novel attractor network model that accounts for the formation of discrete grid modules with specific scale ratios based on geometric relationships.

Findings

Discrete grid modules emerge from hierarchical inhibition and excitation.

Scale ratios between modules naturally fall within observed ranges.

The model's predictions can be tested experimentally.

Abstract

Grid cells in the medial entorhinal cortex (MEC) respond when an animal occupies a periodic lattice of "grid fields" in the environment. The grids are organized in modules with spatial periods, or scales, clustered around discrete values separated by ratios in the range 1.2--2.0. We propose a mechanism that produces this modular structure through dynamical self-organization in the MEC. In attractor network models of grid formation, the grid scale of a single module is set by the distance of recurrent inhibition between neurons. We show that the MEC forms a hierarchy of discrete modules if a smooth increase in inhibition distance along its dorso-ventral axis is accompanied by excitatory interactions along this axis. Moreover, constant scale ratios between successive modules arise through geometric relationships between triangular grids and have values that fall within the observed range. We discuss how interactions required by our model might be tested experimentally.