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. 2007 Aug;26(3):704–716. doi: 10.1111/j.1460-9568.2007.05684.x

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The Authors (2007). Journal Compilation Federation of European Neuroscience Societies and Blackwell Publishing Ltd

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Fig. 4 — Reverse-order reactivation of pyramidal cells during exploration-associated sharp wave/ripples (eSWRs). (A) All the eSWRs in which rank-order regressions produced significant results (P < 0.05) in a recording session are shown. Left (pre-SWR) raster plots in each panel show the firing sequences of cells 3 s before the SWR, while right (SWR) raster plots show firing sequences of the same cells in the 200 ms SWR window. Cells were sorted according to the time of the last spike in the pre-SWR window. In the SWR windows, red and blue raster plots mark negative and positive correlation coefficients, respectively. In some pre-SWR windows blank areas indicate that other SWRs may have occurred in the same window, which were not included to establish pre-SWR spike sequences. (B) Examples of the distribution of regression coefficients (the rank-order regression of cell order vs spike-times) measured in different eSWR events in four different sessions (four different animals). Grey bars show the regression coefficients of the significant cases (P < 0.05), while the non-significant cases are shown in white. (C) Group result showing the significance levels (Z-test) of different sessions. The Z-test was used to test whether within a session significantly more eSWR had negative correlation coefficients than positive ones. Significant sessions are marked in grey. (D) Shuffling of spike order resulted in fewer negative correlations in all 500 shuffling sessions (blue histograms) than the original session (red bar). The same sessions are shown as in (B). (E) Histogram of significance levels for the 500 shuffling trials, measured as the number of shuffled trials that resulted in more negative correlations than the original, divided by the number of shuffling trials (500). (F) Comparison of density histograms of correlation coefficients (red) with the averaged histogram of shuffled sessions (500 shuffled sessions). The same correlation coefficients are shown as in (B) using different binning intervals. (G) Probability values of the Kolmogorov–Smirnov test for different sessions, comparing the average shuffled and original histograms. The Kolmogorov–Smirnov test was used in each session to test whether the shuffled and original histograms were significantly different.