Provided by Cognitive Sciences ePrint Archive
From Grids to Places
M. Franzius*, R. Vollgrafl^, L. Wiskott*
August 28, 2006
Hafting et al. (2005) described grid cells in the dorsocaudal region
of the medial enthorinal cortex (dMEC). These cells show a strikingly
regular grid-like firing-pattern as a function of the position of a rat
in an enclosure. Since the dMEC projects to the hippocampal areas
containing the well-known place cells, the question arises whether
and how the localized responses of the latter can emerge based on
the output of grid cells. Here, we show that, starting with simulated
grid-cells, a simple linear transformation maximizing sparseness leads
to a localized representation similar to place fields.
As reported by Hafting et al. (2005) grid cells in the dMEC show spatial firing
patterns in the form of hexagonal grids with frequencies within one octave (39
to 73 cm mean distance), random phase shifts, and random orientations. The
firing patterns of place cells in the hippocampus, on the other hand, are localized
spots Muller (1996). Our hypothesis is that the latter can be generated from
the former simply by Sparsification, which is consistent with evidence that firing
patterns in hippocampal regions CAl and CA3 are sparser than in enthorhinal
cortex (O’Reilly and McClelland, 1994).
* Intitute for Theoretical Biology, Humboldt-University, Berlin, Germany;
{m.franzius, l.wiskott}βbiologie.hu-berlin.de
fDepartment of Computer Science, Technical University of Berlin, Germany; vroβcs.tu-
berlin.de