This version of the oscillatory-interference model predicted that any increase in grid spacing would be accompanied by a

decrease in the modulation BMN673 of the theta frequency and interspike interval by running speed (Burgess, 2008 and Jeewajee et al., 2008). Consistent with this prediction, the loss of HCN1 results in a profound decrease in the modulation of the theta and intrinsic firing frequency by running speed (Giocomo et al., 2011); however, recent in vitro work demonstrating lack of systematic frequency changes in membrane-potential oscillations near theta frequency suggests that the voltage-dependent change must occur at the level of global, rather than single-cell, oscillatory processes (Yoshida et al., 2011). The degree to which this in vivo reduction in the speed modulation of frequencies matches what would be predicted by the original oscillatory-interference models should be examined in future theoretical work. The strong direct projections from entorhinal

cortex to the hippocampus implied from the beginning that PF-02341066 cost place fields might be generated from the combined input of many grid cells (Fuhs and Touretzky, 2006, McNaughton et al., 2006, O’Keefe and Burgess, 2005 and Solstad et al., 2006). Both computational and experimental studies have begun an attempt to parse out the mechanisms and nature of the interaction between space-responsive neurons in the hippocampus and entorhinal cortex. The linear transformation of several grid fields can easily construct a localized pattern like the firing field of a place cell (Fuhs and Touretzky, 2006, Hafting et al.,

2005, McNaughton et al., 2006, O’Keefe and Burgess, 2005 and Solstad et al., 2006), and the hippocampal firing field would be expected to exhibit dorsoventral scale topography similar to that of the MEC (Brun et al., 2008 and Kjelstrup et al., 2008). A mathematical model proposed by Solstad et al. (2006) mapped out the parameters required for the successful construction of a single place field. First, to avoid similar periodicity in the place signal as in the grid signal, it was suggested that the integration must occur across a moderate Amisulpride number of grid frequencies. Different frequencies then cancel out, and a single peak could be generated if the environment is not very large. The fact that dorsal hippocampal place fields decrease in size after lesions of the ventral and intermediate parts of MEC (Van Cauter et al., 2008) is consistent with the proposed convergence of input from grid cells covering a range of grid frequencies. Second, to produce multidirectional place fields and reduce extrafield place cell firing, most models integrate output from grid cells with more than one grid orientation onto each individual place cell (Molter and Yamaguchi, 2008, Savelli and Knierim, 2010 and Solstad et al., 2006).