Role of deep breaths in ultrasonic vocal production of Sprague-Dawley rats

Abstract

Deep breaths are one of three breathing patterns in rodents characterized by an increased tidal volume. While humans incorporate deep breaths into vocal behavior, it was unknown whether nonhuman mammals use deep breaths for vocal production. We have utilized subglottal pressure recordings in awake, spontaneously behaving male Sprague-Dawley rats in five contexts: sleep, rest, noxious stimulation, exposure to a female in estrus, and exposure to an unknown male. Deep breaths were produced at rates ranging between 17.5 and 90.3 deep breaths per hour. While overall breathing and vocal rates were higher in social and noxious contexts, the rate of deep breaths was only increased during the male’s interaction with a female. Results also inform our understanding of vocal-respiratory integration in rats. The rate of deep breaths that were associated with a vocalization during the exhalation phase increased with vocal activity. The proportion of deep breaths that were associated with a vocalization (on average 22%) was similar to the proportion of sniffing or eupnea breaths that contain a vocalization. Therefore, vocal motor patterns appear to be entrained to the prevailing breathing rhythm, i.e., vocalization uses the available breathing pattern rather than recruiting a specific breathing pattern. Furthermore, the pattern of a deep breath was different when it was associated with a vocalization, suggesting that motor planning occurs. Finally, deep breaths are a source for acoustic variation; for example, call duration and fundamental frequency modulation were both larger in 22-kHz calls produced following a deep inhalation. NEW & NOTEWORTHY The emission of a long, deep, audible breath can express various emotions. The investigation of deep breaths, also known as sighing, in a nonhuman mammal demonstrated the occasional use of deep breaths for vocal production. Similar to the human equivalent, acoustic features of a deep breath vocalization are characteristic.

Reduced emission of alarm 22-kHz ultrasonic vocalizations during fear conditioning in rats lacking the serotonin transporter

“…Moreover, little is still known about sex differences in the acoustic features of 22-kHz USV and few data on 22-kHz USV recorded under standardized conditions in response to air puffs or electric foot shocks are available. It is currently unclear whether such sex differences simply reflect anatomical differences between males and females, such as body weight, lung capacity and vocal tract length (Hegoburu et al, 2011;Inagaki et al, 2012;Riede et al, 2020), or whether they serve communicative functions, for instance through providing additional features by which listening conspecifics may be able to determine the sex of the vocalizing rat, as suggested by Blanchard et al (1992).…”

Rat ultrasonic vocalizations and novelty-induced social and non-social investigation behavior in a seminatural environment

“…It should be mentioned, though, that the advances in research techniques have now made it possible to study this possibility in more detail and resulted in the conclusion that USVs are not just simply a byproduct. Evidence showed that the emitted USVs are indeed tightly linked to locomotion [25], breathing [44] and cardiovascular function [43], and they are even interlocked with active sniffing [45].…”

“…and a new call type can be started at any point during the exhalation phase [44,46,47]. It should be taken into account, though, that if USVs are more than just a by-effect of arousal, there should be more information in nuances of the vocal communication, as they have an extensive USV 'vocabulary' [48,49]).…”

Ultrasonic Vocalizations Emission across Development in Rats: Coordination with Respiration and Impact on Brain Neural Dynamics

“…As mentioned earlier, USV are emitted during the expiratory phase of the respiratory cycle [ 12 , 64 , 104 , 105 , 106 ]. In the 22-kHz USV of adult rats, the length of the expiratory phase is correlated with the length of the USV and is significantly longer than the silent expiratory phases [ 4 , 12 ], suggesting that emitting USV lengthens the expiratory phase, and it is possible that the USV duration is limited by the physiological need to breathe [ 107 ]. Similarly, longer lower-frequency infantile USV are also correlated in length with the expiratory phase of the respiration [ 4 ].…”