Fig. 2.

Ultrasonically associative freezing behavior is disrupted in Piezo2-cKO mice. (A) Paradigm of sound-cue–associated freezing behavior. Pure-tone sound at 16 or 63 kHz played by a TDT ES1 (free field) electrostatic speaker was used as the conditional stimulation, and footshock was used as the unconditional stimulation. (B) Representative examples of locomotion of control mice and Piezo2-cKO mice before (gray, 30 s), during (red, 10 s), and after (blue, 30 s) the pure-tone sound cue at 90 dB SPL. The mice had been trained to pair either 16-kHz cue or 63-kHz cue with the footshock-induced freezing. Dots indicate the location of the mouse every 0.5 s. Pax2^Cre mice, Atoh1^Cre mice, and Piezo2^f/f mice were used as controls (C and D). Freezing time in percentage is shown with 16-kHz cue (C) or 63-kHz cue (D). In D, experimental data from two Pax2^Cre;Piezo2^f/f mice were omitted because during testing, no locomotion was detected in these animals. Kruskal–Wallis test, P = 0.225 in C; one-way ANOVA, ****P < 0.0001 in D; error bars, SD. For C and D, N numbers are shown in panels. All the mice were ∼1 mo old.