Fig. 1: During freezing, regular 4 Hz breathing entrains the olfactory bulb.
a Experimental protocol and behavioural results: median percentage of time spent freezing for all mice during the CS− and CS+, grouped as blocks of four sounds (4CS− followed by 12 CS+). Sound block significantly affected freezing rates (Friedman test: X2(3) = 19.6, p = 2.01e−4). Post-hoc analysis revealed significant differences of the CS+ blocks compared to the CS− block (Wilcoxon signed-rank test: Signed Rank statistic = 0,14,23; p = 6e−5, 0.0067, 0.0353, n = 15). b Illustrative example of breathing activity as recorded in the plethysmograph and OB and dmPFC LFPs during exploratory and freezing periods. Note the striking regularity and synchronicity in the 3–6 Hz range in all three time courses during freezing. c Distribution of breathing frequencies recorded in the plethysmograph during freezing and non-freezing periods. (n = 6). d Mean breathing tidal volume during freezing and non-freezing periods. (Paired Wilcoxon signed-rank test: Signed Rank statistic = 0, p = 0.0312, n = 6). e, f Variability of breathing frequency and tidal volume during freezing and non-freezing periods. (Paired Wilcoxon signed-rank test: Signed Rank statistic = 0,0; p = 0.0312, 0.0312, n = 6). g Averaged OB LFP power spectra during freezing (blue) and non-freezing (grey) periods. Error bars are SEM. Inset: average signal-to-noise ratio of 3–6 Hz band during freezing and non-freezing periods. The signal to noise ratio is defined as the ratio between power in the band of interest to the power in the rest of the spectrum. (Paired Wilcoxon signed-rank test: Signed Rank statistic = 0, p = 6.10e−4, n = 15). h Averaged coherence between breathing and the OB during freezing (blue) and non-freezing (grey) periods. Error bars are SEM. Inset: average coherence of 3–6 Hz band during freezing and non-freezing periods. (Paired Wilcoxon signed-rank test: Signed Rank statistic = 0, p = 0.0312, n = 6). In all panels, boxplots show the median and interquartile.
