Figure 2.

A Subpopulation of GCs Shows Spatially Tuned Place Cell Activity

(A) Top, AP rate map of an active GC. The abscissa represents the position on the linear belt (2-cm spatial binning), and the ordinate denotes the lap number. The number represents the mean AP rate (top), and the color-code bar indicates the AP rate in spatial bins (right). Bottom, plot of average AP frequency against the position across laps. This GC fires consistently at a position of 80–130 cm.

(B) Left top, V_m median (after AP removal) plotted against the position in the same cell. The color code indicates Z-scored V_m values. Left bottom, plot of V_m median against the position across laps. Right top, V_m variance (after AP removal) plotted against the position in the same cell. The color code indicates V_m variance. Right bottom, plot of V_m variance against the position across laps. Note more depolarized V_m and higher V_m variance at a specific location.

(C) Spatial tuning of subthreshold EPSP activity. Left, polar plot of EPSP event frequency. Spatial positions (0–180 cm) were converted into angles (0°–360°). Black circles represent EPSP event frequency in each bin (number of events divided by time spent in the respective bin), and the red arrow indicates the mean EPSP frequency tuning vector (multiplied by 10 for illustration purposes). Right, distribution of mean tuning vector length (TVL) from shuffled data. The red vertical line indicates the mean TVL of the original data. The mean TVL from the original data is significantly larger than the values obtained from the shuffled data.

(D–F) Similar data as shown in (A)–(C) but for another GC with spatially tuned firing.

(G–I) Similar data as shown in (A)–(F) but for another GC with spatially tuned firing.

(J–L) Similar data as shown in (A)–(I) but for a CA1 pyramidal neuron.

(M) Left, proportion of active GCs with spatially tuned AP output. 3 of 31 cells were classified as place cells. Right, proportion of CA1 pyramidal neurons with spatially tuned AP output. 5 of 17 cells were classified as place cells.

(N) Proportion of place GCs with spatially tuned input. 3 of 3 cells showed spatially tuned EPSPs.