Figure 1.
Sparse but Heterogeneous Firing of GCs in Head-Fixed Mice during Spatial Navigation
(A) Scheme of experimental configuration. Mice were running on a linear belt while simultaneous whole-cell patch-clamp and LFP recordings were made.
(B) Location of GC cell bodies along the upper-lower blade axis (top) and along the inner-outer GC layer axis (bottom). Green line, active GCs; blue line, silent GCs. Distance was normalized to maximum value.
(C) Recording from an active GC, which fired a mixture of single APs and bursts. Left, reconstruction of soma and dendrites of the GC filled with biocytin during recording. Right, Vm (top), LFP (center), and velocity (bottom) (dotted horizontal line indicating zero velocity) versus experimental time.
(D) Similar to (C) but for a silent GC that did not fire APs during the 22-min recording period.
(E) Maximum branch order (left) and number of branches for each branch order (right) in active versus silent GCs. Active GCs show a significantly higher maximal branch order and a larger number of higher-order branches in comparison to silent GCs. ∗∗∗ indicates p < 0.001.
(F) Summary pie chart of the fraction of active and silent GCs during 5–30 min recording periods. In total, recordings were made from 73 morphologically identified GCs.
(G) Histogram of average AP frequency in active GCs. The red line indicates log-normal distribution fit to the data. AP frequency varies over three orders of magnitude.
(H) Summary bar graph of AP frequency during theta versus nontheta periods (left) and running versus immobile periods (right). Boxplots show lower quartile (Q1), median (horizontal line), and upper quartile (Q3). The interquartile range (IQR = Q3–Q1) is represented as the height of the box. Whiskers extend to the most extreme data point that is no more than 1.5 × IQR from the edge of the box (Tukey style). Red crosses illustrate outliers. n.s., not significant.
(I) Polar plot of phase preference of APs in active GCs in relation to theta (left) and gamma (right) oscillations. The red arrow indicates the mean tuning vector. Representative LFP traces band-pass filtered in the theta and gamma frequency ranges are shown on top. APs were significantly phase locked to both theta and gamma oscillations.