Figure 3. Two correlates of cycling.

(A-D) Time-averaged firing maps (left) and rasters (right) of four example cells (recording regions at far left). Data plotted is from a single type of maze pass (colored arrows; grey: outbound; pink: inbound). In rasters, maze pass times are indicated above plots by colored bars; plotted above each pass is theta-filtered LFP (θ, 5–11 Hz from CA3). Firing maps, left column: positions visited (grey) and positions where the cell fired (black points). Total number of spikes is reported at upper right. Firing maps, right column: time-averaged firing map. Peak firing rate is reported at upper right. For the cell in (B), data from two types of maze passes are shown on separate rows to illustrate that firing patterns for an individual cell could depend on condition.

(E) Firing auto-correlograms (ACGs) of the four cells from (A-D). Each ACG (5-ms bins; zero bin excluded) is smoothed with a Gaussian kernel (σ = 10 ms) and peak-normalized. Total number of spikes in ACG is reported at top. For the cell from (B), data from each of the two types of maze passes are shown on two separate rows.

(F) Firing ACGs of all cell samples (in rows) across recording regions (CA1, CA2, CA3). Greyscale indicates firing density. Each cell sample corresponds to data from a single cell for one type of maze pass. Cell samples are ordered by cycle skipping index (CSI; high to low plotted top to bottom); for each region, red arrowheads indicate division between cell samples with CSI > 0 (above division) vs. < 0 (below division). CSI < 0 corresponds to classical firing (firing on adjacent cycles), while CSI > 0 corresponds to cycle skipping.

(G) Cycle skipping index (CSI) by hippocampal recording region. Top, diagram of sub-regions with higher CSI values (CA2 and CA3; yellow zone). Bottom, histograms of CSI values across cell samples. Total number of cell samples is indicated at upper right. Values in CA2/CA3 were higher than in CA1.

(H) CSI by behavioral condition. Top, schematic of the conditions (choice passed: periods when subject was leaving the choice point; choice imminent: periods when subject was approaching the choice point). Bottom, histograms of CSI values across cell samples. Total number of cell samples is indicated at upper right. For every recording region (CA1, CA2, CA3), CSI values were higher for choice imminent vs. choice passed.

Rank-sum tests.

P-values reported in main text.

**, P < 0.01.

***, P < 0.001.