Fig. 6: Optogenetic stimulation of PV-expressing MS neurons evokes tSC-like activity patterns in the CA1.

a Left, schematic of the acute experiment with optogenetic stimulation of PV-expressing MS neurons in awake mice. Right, raw LFPs recorded from the CA1 radiatum layer (black) during photostimulation of MS PV-expressing neurons. Blue ticks mark 2 ms laser pulses. Stimulation was performed in theta-modulated bursts of laser pulses (tmS) mimicking the different frequencies of physiological tSCs (22 Hz, 35 Hz, 54 Hz, 80 Hz). b Mean amplitude of supra-theta spectral components as a function of theta phase during the different tmS protocols. Two theta cycles are shown, indicated by the white cosine curves. c Spike rasters and peri-stimulus time histograms of a putative CA1 interneuron aligned to the onset of each tmS sorted by stimulation frequency (blue lines, photostimulation). Note the brief initial suppression of spiking upon photostimulation before the firing rate increase (see also Supplementary Fig. 16). d Laminar profile of currents related to spontaneous tSCs. Left, schematic of a pyramidal cell showing CA1 layers (str. py., stratum pyramidale; str. rad., stratum radiatum; str. lac. mol., stratum lacunosum moleculare). Stoyo, Karamihalev. (2020). CA1 pyramidal neuron. Zenodo. https://doi.org/10.5281/zenodo.4312494. Right, mean amplitude of supra-theta CSD signals as a function of theta phase from an example session of a freely moving mouse (see also Supplementary Fig. 17 for the same analysis on cycles strongly expressing a particular tSC). Note that the upper limit of the y-axis is extended in the stratum pyramidale panel to visualize fast gamma-bands. White cosine curves, two theta cycles are shown. e Mean amplitude of supra-theta CSD signals as a function of theta phase during different tmS protocols, showing the laminar profile of currents related to photostimulation-evoked tSCs. White cosine curves indicate the theta phase defined from the radiatum layer LFP. f Schematic of the experiment using SwiChR injected into the CA1 and an optic fiber implanted into the MS. g Proportion of theta cycles expressing tSCs during inhibition and control periods. Data points belonging to the same recording session (n = 23) are connected with gray lines. Box-whisker plots show median, interquartile range and non-outlier range. **p = 0.0015, two-sided Wilcoxon signed-rank test. Source data are provided as a Source Data file.