Figure 4. Constant cycling (8 Hz) of possible future locations.

Three example maze passes (A, B, C) from a single recording epoch.

(At left) Behavior plot. Position (green) and head angle (black lines; sampling period in plot: 133 ms) are overlaid on positions visited by the subject in epoch (color-coded by maze arm; grey: C (center); blue: L (left); red: R (right)).

(At right) Data and decoded representation. Top section: LFP (θ, 5–11 Hz; CA3). Second section: decoded output (y-axis: linearized position); probability density is plotted as color values and colored by maze arm (black: C; blue: L; red: R); green line indicates actual position of subject. In (A), several example instances of ~100 ms spatial sequences within the center arm (schematized in Figure S1C) are highlighted by open arrowheads. Third section: multi-unit spiking activity (MUA; smoothed with Gaussian kernel (σ = 20 ms)). Bottom section: linear (light grey fill trace) and angular (dark grey fill) speed.

(D) Prevalence of constant cycling in observed (red line) vs. shuffled data (histogram, 10000 permutations; study-wide shuffle). Plotted is the total number of cycles in detected constant cycling periods. P = 0.0034 (34 out of 10000 shuffles had equal or higher prevalence of cycles).

(E) P-values of individual constant cycling periods (individual period shuffle). Shaded area enclosed by dotted line indicates criterion (P < 0.05) for individual periods analyzed subsequently in (F) and (G). Plotted separately are individual periods that occurred exclusively during movement (>4 cm/s) (black bars) versus those that overlapped with low speed periods (<4 cm/s for <0.5 s) (stacked white bars).

(F) Histogram of durations (in cycles) of individual constant cycling periods. Bar plot convention follows that of panel (E).

(G) Behavioral speed during individual constant cycling periods. Individual periods that occurred exclusively during movement (>4 cm/s) (black dots) versus those that overlapped with low speed periods (<4 cm/s for <0.5 s) (open grey circles) are plotted separately. Observed periods commonly occurred when angular speed was low (<10 deg/s), indicating that constant cycling could occur in the absence of overtly deliberative behavior (e.g. head scanning (Johnson and Redish, 2007; Redish, 2016)).

(H) Theta phase histograms of decoded location representation (n = 1683 maze passes across 7 subjects; SEM omitted from plots due to minimal size). For each maze pass, posterior density (across positions) was pooled across time bins, subdivided into three maze arms (center, choice, and alternative (alt)), then histogramed by theta phase. Decoded data restricted to the center arm. Note that both choice and alternative arms tended to be represented in the second half of theta (0 to π).

(Left) 12-bin histogram: center, choice, and alternative (alt).

(Upper right) 2-bin histogram: center vs. choice.

(Lower right) 2-bin histogram: center vs. alternative (alt).

Signed-rank tests.

P-values reported in main text.

***, P < 0.001.