Figure 3.

Spike-time autocorrelations of MEC grid cells from mice moving in virtual corridors. A, visual inspection of spike-time autocorrelations suggests a separation in two major groups, SB and bursting. Based on the intracellular measurements (see Fig. 1), the group of bursting neurons can be subdivided in cells with DAP (BD⁺), which are shown in red, and cells without detectable DAP (BD^–), shown in yellow. The arrows mark the example neurons shown in Figure 1. One cell has intermediate properties and is assigned to the sparsely-bursting group (blue) by k-means clustering (k = 2). B, Mean autocorrelation. Shaded areas show the variability in the data (SD). C, The first two principal components of the spike-time autocorrelations. The pronounced peaks in B, C demonstrate that ISIs of around 4 ms are indicative of both the mean grid-cell discharge patterns and their cell-to-cell variability.