Measurement of ultrasonic vocalizations (USV) provides a unique and gentle method to study social behavior in rodents. Mice emit ultrasonic vocalizations in different social contexts throughout their lifespan, including pups when separated from the dam and adult males when exposed to a sexually receptive female. In the latter context, male mice typically emit ultrasonic vocalizations of 30 to 110 kHz. These vocal emissions are considered as an index of emotionality, social interest, and motivation.
To measure social communication deficits, we used Fmr1-KO mice, a model of autism spectrum disorder that is known to present a wide range of behavioral abnormalities such as an unusual social phenotype. USV emission recordings were established using male Fmr1-KO and control C57BL/6 animals at the age of 10 weeks, when exposed to urine of sexually receptive females. Vocalizations were recorded for 5 minutes with the Avisoft technology under red light conditions. The total number of vocalizations and the latency to initiate the first call were measured for the whole 5 minutes of the recordings.
Results of the USV recordings showed a significant decrease in the number of vocalizations of Fmr1-KO compared to control C57BL/6 mice (Figure 1). However, the latency to initiate the first call did not change (data not shown).
Figure 1. Number of ultrasonic vocalizations. Number of vocalizations during a 5-minute recording session. n=15 per group; mean + SEM by students’ t-test followed by Mann-Whitney’s post hoc test; **p<0.01.
The measurement of ultrasonic vocalizations can be easily adjusted to evaluate other mouse models, mice in different social contexts, or even rats.