Extended Data Figure 4: Analysis of theta modulation.

a, Examples of power spectral density (PSD) plots from two CA1 cells, showing a prominent theta oscillation. Black trace, median across trials. Shaded area shows estimated s.e.m. across trials. The position of the peak in the median PSD is indicated. b, Distribution of theta frequencies across all 56,496 trials in five rats with CA1 recordings. Red marks show median values for each of the rats. c, Phases of theta at which spikes were fired by the same neurons as in a, showing theta phase precession. Black dots, individual spikes plotted in time (linearly warped between the press and the release of the joystick) and theta phase. Each spike is plotted twice with a 2π phase offset. Red line, linear regression fit to the data. d, Slopes of the regression fits quantified in c for all 138 CA1 cells that had a significant correlation (P < 0.01) between theta phase and warped time. Negative slope indicates forward phase precession, as is typically observed during spatial navigation. e, Frequency of theta oscillations (mean ± s.e.m. across rats) quantified across trials that had different average ‘speeds’ of sound frequency traversal in the SMT. Red line shows linear regression fit; the slope of the fit was not significantly different from 0 (P = 0.70). Unlike in spatial navigation, theta frequency did not correlate to speed; this may imply that the relationship between theta and speed during navigation is dependent on locomotion-related signals.