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. 2013 May 7;8(5):e63590. doi: 10.1371/journal.pone.0063590

Figure 3. Effects of fear conditioning on heart rate and heart rate variability.

Figure 3

(A) Illustration of a fear conditioning chamber for producing a tone-shock pairing fear memory. (B) A 30-sec neural tone (85 dB, 5000 Hz) co-terminates with a 2-sec mild foot shock (0.75 mA). (C) Schematic representation of experimental paradigm for cued fear conditioning. (D) Instant HR responses of an individual mouse during three CS-US pairings, trial#1, trial#4 and trial#7. The freezing responses were plotted on top of the instant HR; freezing state, red bar; non-freezing state, blue bar. The blue vertical lines indicate the onset and offset of the tone (30 seconds); the red vertical line indicates the onset of the foot shock (2 seconds). (E) Poincaré plots of the same mouse’s R-R intervals of 28-sec tone duration in trial#1, trial#4 and trial#7. (F) The average HR of 28-sec tone duration during training. (G) The average CV of instant HR of 28-sec tone duration during training. (F) The average freezing responses of 28-sec tone duration during training. Error bars, s.e.m.; n = 11; ***P<0.001, one-way repeated measures ANOVA and Tukey post hoc test.