Fig. 4. Speed representation in an open field.
(A) Rate maps (left), z-scored running speed (gray) and firing rate (color) (middle), and mean firing rate as a function of running speed (right). Each row shows the firing patterns of a single neuron. Numbers, peak firing rates in the figure (left and middle) and speed scores (right). (B to E) Cumulative distribution of Ispike (B), mean firing rates (C), Isec (D), and speed scores (E). P values: Wilcoxon rank sum test. (D and E) Gray curves, numbers, and dotted lines, the distribution of shuffled data and its 1st (E) and 99th (D and E) percentiles. *P = 0.019 and ****P < 0.0001, CA1 versus SUB neurons exceeding either the 1st or 99th percentile threshold, Wilcoxon rank sum test. (F) Example decoding of speed from simultaneously recorded CA1 (top) and SUB (bottom) neuron activity. Gray, observed speed. Color, decoded speed. Numbers, decoding accuracy. (G) Decoding accuracy averaged across all animals. Dashed-dotted line, SUB decoding accuracy calculated after randomly removing spikes from SUB neurons to match the CA1 mean firing rate (mean). Black line, decoding error obtained from a shuffling procedure. (G and H) Means (solid lines) ± SD (shaded areas). (H) Normalized decoding accuracy after randomly removing (negative x values) or adding (positive x values) spikes to each neuron. Group data were averaged across all animals. P < 0.05, Bonferroni test after two-way repeated-measures ANOVA. (I and J) Percentage of n-speed (left) and p-speed (right) cells in the CA1 and SUB (I) and among SUB projection neurons (J). Numbers, number of speed cells to the total number of neurons. (I) ***P = 0.0002, χ2 test. (J) Dotted lines, percentage of n-speed (left) and p-speed (right) cells in SUB neurons. *P < 0.05, bootstrap analysis.