Syllable timing and shapes predicted by underlying breathing patterns in mouse ultrasonic vocalization

Abstract

Mouse ultrasonic vocalizations (USVs) exhibit a wide range of shapes and lengths, posing challenges in clustering the syllables into distinct groups. The underlying mechanism responsible for such variability remains unknown. However, recent studies have suggested an association between USV syllable length and breathing speed. In this study, we monitored the breathing patterns of adult male mice during interactions with females to explore the temporal relationship between breathing and USV production. We recorded two signals simultaneously: the local field potential (LFP) signal from the olfactory bulb (OB) and the temperature signal reflecting the direction of nasal airflow. Our findings reveal that the breathing pattern underlies both the timing and shape of USV syllables. Firstly, we analyzed the positioning of USV syllables within the breathing cycle and established a strong association between syllable length and the speed of breathing rhythm. For instance, faster breathing rhythm involved shorter vocalizations. In addition, the onset of syllables were phase-locked to a certain window within the breathing cycle, while longer syllables spanned a larger portion of the cycle. Interestingly, OB LFP signal and temperature signal exhibited distinct temporal profiles with respect to USV syllables. Secondly, to assess the extent to which variations in syllable shapes could be predicted from the underlying breathing pattern, we performed clustering analyses on OB LFP and breathing traces, grouping syllables occurring during specific breathing patterns. Although syllable shape cannot be deterministically predicted due to the inherent variation in various parameters, the information derived from the breathing pattern accounted for a significant portion of the variation in syllable frequency modulations. In conclusion, our study provides compelling evidence that the breathing pattern plays a pivotal role in determining the timing and shape of USV syllables in mice. Understanding the intricate relationship between breathing and vocalization may shed light on the underlying mechanisms of vocalizations in mammals.