Ultrasonic Vocalizations in Mice During Exploratory Behavior are Context-Dependent

Abstract

While rat ultrasonic vocalizations (USVs) are known to vary with anticipation of an aversive vs. positive stimulus, little is known about USVs in adult mice in relation to behaviors. We recorded the calls of adult C57BL/6J male mice under different environmental conditions by exposing mice to both novel and familiar environments that varied in stress intensity through the addition of bright light or shallow water. In general, mouse USVs were significantly more frequent and of longer duration in novel environments. Particularly, mice in dimly-lit novel environments performed more USVs while exhibiting unsupported rearing and walking behavior, and these calls were mostly at high frequency. In contrast, mice exhibited more low frequency USVs when engaging in supported rearing behavior in novel environments. These findings are consistent with data from rats suggesting that low-frequency calls are made under aversive conditions and high-frequency calls occur in non-stressful conditions. Our findings increase understanding of acoustic signals associated with exploratory behaviors relevant to cognitive and motivational aspects of behavior.

Keywords: exploration; mouse; novelty; rearings; ultrasonic vocalizations (USVs).

Figure 1

Schematic representation of experimental procedure. On day 1, for the familiar groups, mice were pre-exposed to the open field under dim light for 30 min. On the test day, novel groups were exposed to the open field for the first time in two lighting conditions: dim (Blue: 20–40 lux) and bright (Yellow: 400–500 lux). USVs were recorded for the first 5 min. Box without lines represents Novel and Box with the lines represents Familiar conditions. Each arrowed bar represents 30 min. A red bar represents 5 min. USVs: ultrasonic vocalizations.

Figure 2

Ultrasonic vocalizations (USVs) in adult male mice. Box and whisker plots represent (A) total number of USVs, (B) number of high frequency calls (>35 kHz), and (C) number of low frequency calls (20–35 kHz) were displayed. For the acoustic features, (D) mean peak frequency, (E) call duration, and (F) distribution of calls with frequency and call durations were shown peak in each environments, including ND, novel dim; NB, novel bright; FD, familiar dim; FB, familiar bright; and water. ^*P < 0.05, ^***P < 0.001 (Bonferroni post-hoc analysis; Two-way ANOVA).

Figure 3

Acoustic characteristics of calls emitted in behaviors in novel dim and novel bright contexts. (A)Calls durations and (B) Peak Frequency of calls in all conditions. (C) Percent time mice engaged in the behaviors “supported rearing,” “unsupported rearing,” “self-grooming,” and “walking” spend making “high-frequency (HF)” and “low-frequency (LF)” calls. Data are presented as means ± SEM. ^***p < 0.0001—in comparison with “Novel Bright” condition (Bonferroni post-hoc analysis; Two-way ANOVA).