Hardcastle, Kiah Grid Cells Oct 31 2014
<p>Oct 30, 2014 09:28 PM</p>
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Fri Sem today;</p>
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<b>Medial entorhinal grid cells</b> fire in periodic, hexagonally patterned locations and are proposed to support <b>path-integration based navigation</b>. </p>
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The<b> recursive nature of path-integration results in accumulating error</b> and, without a corrective mechanism, a breakdown in the calculation of location.</p>
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The observed long-term stability of grid patterns necessitates that the system either performs highly precise internal path-integration or implements an external landmark-based error correction mechanism. To distinguish these possibilities, we examined grid cells in behaving rodents as they made long trajectories across an open arena. We find that error accumulates relative to time and distance traveled since the animal last encountered a boundary. This error reflects coherent drift in the grid pattern. Further, interactions with boundaries yield direction-dependent error correction, suggesting border cells serve as a neural substrate for error correction. These observations, combined with simulations of an attractor network grid cell model, demonstrate that landmarks are crucial to grid stability.
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