(2007) (Figure 1D). To account for the variability of the firing rate in consecutive recordings under the same conditions (Hargreaves et al., 2005, Leutgeb et al., 2007 and Fyhn et al., 2007), we Selleckchem BAY 73-4506 emulated the effect of undersampling of the space, an unavoidable condition given the experimental protocols. To account for the effect of undersampling, we introduced a stochastic factor in every comparison with a variance dependent on the rate (see Experimental Procedures). The level of the correction was obtained by fitting to the experimental data (PV correlation) of two subsequent recordings

obtained under the same condition (Figure S3). We observed an exponential-like decay shape for the correlation curves with the global level of decorrelation monotonically and positively affected by the level of influence of the LEC input (regulated by α). A value of α = 0.32 (Figure 1D) gave the best fit. With the value of α determined, we could then examine how morphing affected rate remapping. First, we investigated whether the simulated place fields have properties that match those experimentally CHIR-99021 in vivo observed. We found that simulated granule cells have multiple place fields (average of 2.2 place fields) and have a mean place field size of 943 cm2. The distribution of the number of place fields in each active

cell was similar to experimental measurements (Figure 1E, t = 0.98, p < 0.0005). The place field size is also in accord with data (analysis of Leutgeb et al., 2007 by de Almeida et al., 2009a). We also tested whether the observed restricted diversity of grid cell activity (Barry et al., 2007) affects the results of our simulation. When the grid cell proprieties were limited to one orientation and three grades of spacing, no significant difference in the whatever distribution of the number of place fields (Wilcoxon, p = 0.65) or the PV

correlation (Student’s t test, two-tailed, p = 0.31) was found. These results are not unexpected given previous work showing that MEC input alone can account for these properties; what is added here is the demonstration that the LEC inputs, when included in the model, do not interfere with place cell formation in the DG by the MEC inputs. We next directly compared the remapping of individual place fields of our simulation of morphing with the results obtained by Leutgeb et al. (2007) (Figure 2A). The experimental results show that all place fields of the same cell remap and do so independently; thus, one field may increase its firing rate during morphing while the other decreases its rate. Figure 2B shows this to be similarly true in our simulated place fields. Moreover, the relative proportion of remapping patterns that exhibit a significant fit for linear, quadratic, and sigmoidal functions could not be distinguished from the experimental observations (Figure 2C, t = 0.93, not significant [n.s.]).