Fig. 1: Supra-theta spectral components in the MS and the hippocampal CA1 radiatum layer of freely moving mice.

a Top, schematic of dual silicon probe recordings from the hippocampal CA1 region and the MS. Bottom, example of synchronously recorded CA1 LFPs and MS extracellular spike rasters. b Inter-spike interval histogram of an example MS neuron (top) and average of all recorded MS neurons (bottom, n = 365 neurons from 6 awake mice). c Power spectrum of an example MS neuron (top) and average of all recorded MS neurons (bottom, n = 365). d Top, normalized average wavelet spectrogram of an example MS spike train (convolved by a Gaussian window, see Methods) triggered on first spikes of bursts. Bottom, average coherence between MS spiking and CA1 LFP triggered on first spikes of bursts of an example MS neuron. Spectrograms were normalized by the mean power for each frequency, thus visualizing the spectral changes around the triggering event. e Example theta cycles dominated by different tSCs. Black, raw LFP signal; red, theta band signal; brown, supra-theta signal extracted by EEMD. Blue, green, purple and orange lines show the dominant tSCs in each example cycle. f Mean amplitude of supra-theta spectral components as a function of theta phase was computed from the raw LFP of an example session, for all cycles (top left) and for cycles strongly expressing a given tSC. Two theta cycles are shown, indicated by white cosine curves. g Average power spectrum of tSCs across all sessions. Peak frequencies are shown in the brackets. Error shades show the standard error of the mean. h Frequency of theta cycles expressing different tSCs. i Average proportion of theta cycles expressing each tSC during long theta periods (left), short theta epochs (middle) and around theta segment boundaries (right). Insets show the proportion of theta cycle expressing any of the tSCs. j Speed of mice during theta cycles expressing different tSCs. Box-whisker plots show median, interquartile range and non-outlier range in panels h–j. Differences were tested with two-sided repeated measures ANOVA and Tukey’s post hoc test and significant differences are indicated by the color-coded matrices in (h and j). Source data are provided as a Source Data file.