Extended Data Fig. 1: LFP pacing efficiency and single unit identification.
From: Precisely timed theta oscillations are selectively required during the encoding phase of memory
(a) Pacing efficiency scores for recordings when each mouse explored the open field (top) or rectangular track (bottom). For every 2-s time-window, the peak LFP frequency was calculated for sessions without stimulation (gray bars) and with 12 Hz stimulation (blue bars), and the probability distribution of these peak LFP frequencies was plotted for each animal. Efficient pacing results in a narrow frequency peak at the stimulation frequency, and the pacing efficiency score was therefore defined as the maximum probability (in 0.2 Hz wide bins within 1 Hz of the stimulation frequency) in stimulation sessions. (b) The ratio of the spike waveform peak to trough amplitude (peak-valley ratio) and average firing rate (Hz) for each recorded cell was calculated to determine appropriate cutoff thresholds that separated between putative principal cells (blue circles) and putative interneurons (red circles). For cells recorded from the mEC either on the rectangular track (left) or the open field (middle), we used a rate cutoff of 15 Hz. For cells recorded from the hippocampus (right), we used a combined rate cutoff of 10 Hz and peak-valley cutoff of 1.5. (c) Example of multiple single-unit clusters recorded during the pre-stimulation baseline (baseline 1, left) and during optical stimulation (right). Defined single-unit clusters (red, green and blue) remained stable between sessions without stimulation and with stimulation. (d, top) L-ratio calculated for clusters of single units recorded in the mEC. (d, bottom) Isolation distance values calculated for clusters of single units recorded in the mEC. There was no change in L-ratio [n(B1, 8 Hz, 10 Hz, 12 Hz, B2) = 593, 476, 111, 531, 593 cells from 11 mice, H(4, 2299) = 2.17, P = 0.704, Kruskal-Wallis test] or isolation distance [n(B1, 8 Hz, 10 Hz, 12 Hz, B2) = 580, 462, 109, 518, 579 cells from 11 mice, H(4, 2243) = 7.91, P = 0.095, Kruskal-Wallis test] across stimulation conditions. NS, not significant.
