Fig. 1.

Spike rates and multineuronal spike sequences are correlated during ripple and theta oscillations. (A) Spike rates during ripples and theta are correlated. Each dot indicates the spike rate of one unit (n = 268 pyramidal cells, PYR, and 37 interneurons, INT, from 11 sessions in four freely moving mice), averaged over ≥100 (median, 1,274) ripple events and ≥1,000 (median, 18,250) theta cycles. Numbers: rank correlation coefficients; ***P < 0.005, permutation test. (B) Spike gain (defined as the mean spike rate of a given unit during ripples, divided by the baseline rate; baseline periods include nonripple and nontheta immobility epochs) is correlated during ripples and theta-associated behaviors. (C) Spike sequences during ripples and theta are correlated. For presentation purposes, the rank of each simultaneously recorded unit (12 INT, 43 PYR) during an example session was averaged separately during ripple events (left) and theta cycles (center), and sorted according to the ripple rank; error lines, SEM. Numbers indicate rank correlations based on INT only (blue), PYR only (red), or all cells (black); ***P < 0.005, permutation test. (D) Sequence consistency during ripples, theta, and theta vs. ripples (11 sessions in four mice). Dots, individual sessions; bars, group means (SEM); black dots, sessions with significant (P < 0.05, permutation test) rank correlation (“consistent” sequences); magenta dots, session illustrated in C. ***P < 0.005, Wilcoxon’s signed rank test (zero median null). For details and rationale of this analysis, see Fig. 4. (E) Fraction of sessions with consistent sequences. Dashed line shows chance level; error bars, SEM; ***P < 0.005, exact Binomial test. (F) Sequence consistency is maintained when only INT are considered. */**/***, signed-rank test. (G) When only PYR are considered, sequence self-consistency during ripples and theta is maintained. NS: not significant, signed-rank test, zero-median null.