Figure 2
Ultrasonic vocalizations (USVs) during stroking stimuli. (A,B) Examples of spectrograms of 50-kHz calls (A) and 22-kHz calls (B). (C–H) Time courses of the numbers of vocalizations during stroking in the S3-6 group (C, 50-kHz; D, 22-kHz), S7-10 group (E, 50-kHz; F, 22-kHz), and S3-10 group (G, 50-kHz; H, 22-kHz). In the S3-6 group, the numbers of 50-kHz calls at the ages of 5 and 6 were significantly larger than the number of 50-kHz calls at the age of 3 weeks. In addition, the number of 50-kHz calls at the age of 6 weeks was significantly larger than that at the age of 4 weeks. In the S7-10 group, the number of 50-kHz calls did not significantly change. In the S3-10 group, the numbers of 50-kHz calls at 6, 7, 8, 9, and 10 weeks of age were significantly increased compared to the number at the age of 3 weeks. The numbers of 50-kHz calls at 7 and 8 weeks of age were significantly larger than the number at 4 weeks of age. The numbers of 22-kHz calls during stroking did not significantly change in any of the three groups. †, P < 0.01; *, P < 0.05, post-hoc Holm’s test.
