Acoustical cues for perception of emotional vocalizations in rats

Abstract

The ultrasonic vocalizations of rats can transmit affective states to listeners. For example, rats typically produce shorter calls in a higher frequency range in social situations (pleasant call: PC), whereas they emit longer calls with lower frequency in distress situations (distress call: DC). Knowing what acoustical features contribute to auditory discrimination between these two calls will help to better characterize auditory perception of vocalized sounds in rats. In turn, this could lead to better estimation of models for processing vocalizations in sensory systems in general. Here, using an operant discrimination procedure, we examined the impact of various acoustical features on discriminating emotional ultrasonic vocalizations. We did this by systematically swapping three features (frequency range, time duration, and residual frequency-modulation pattern) between two emotional calls. After rats were trained to discriminate between PC and DC, we presented probe stimuli that were synthesized calls with one or two acoustical features swapped, and examined if the rats judged these calls as either PC or DC. The results revealed that all features were important for discrimination between the two call types, but frequency range provided the most information for discrimination. This supports the hypothesis that while rats utilize all acoustical features to perceive emotional vocalizations, they considerably rely on frequency cues.

Biological Functions of Rat Ultrasonic Vocalizations, Arousal Mechanisms, and Call Initiation

“…These two categories of calls (with some limited variation of frequencies within each category) differ by 2–10-fold in all acoustic parameters [ 236 ] so they are easily discriminated by rats. Although many acoustic features of rat ultrasonic vocalizations may play a role in this discrimination, the sound frequency band proved to be the most informative and critical for this discrimination [ 253 ]. The mean sound frequency of any vocalization and any valence was approximately three times more likely to serve for the proper discrimination of calls than frequency modulation within the call, and 6.5 times more likely to discriminate a call than that based on its duration [ 253 ].…”

“…Although many acoustic features of rat ultrasonic vocalizations may play a role in this discrimination, the sound frequency band proved to be the most informative and critical for this discrimination [ 253 ]. The mean sound frequency of any vocalization and any valence was approximately three times more likely to serve for the proper discrimination of calls than frequency modulation within the call, and 6.5 times more likely to discriminate a call than that based on its duration [ 253 ]. This call discrimination is biologically important because the 22 kHz and 50 kHz vocalizations signal two different emotional states that should be recognized by rats.…”

Correlations across timing cues in natural vocalizations predict biases in judging synthetic sound burst durations

“…As the name implies, alarm vocalizations are used to communicate an alarm to other rodents when they are distressed or alternately when they are defeated during rough and tumble play (Wöhr and Schwarting, 2008; Thomas et al, 1983; Saito et al, 2019). When rodents hear synthetic versions of these alarm vocalizations, they display stereotyped social responses provided the proper combinations of pitch and temporal cues are incorporated (Wöhr and Schwarting, 2008; Saito et al, 2019). Confirming prior studies, natural rodent alarm vocalizations examined here have a pitch or fundamental frequency around 22 kHz (Fig.…”

“… Abstract It is well known that animals rely on multiple sources of information in order to successfully identify sounds in natural environments, to make decisions that are optimal for their survival. For example, rats use duration and pitch cues to respond appropriately to prosocial and distress vocalizations (Saito et al, 2019). Vocalization duration cues are known to co-vary with other temporal cues (Khatami et al, 2018), yet little is known about whether animals rely upon such co-variations to successfully discriminate sounds.…”

The Affective Disorder Test: a new test to assess depression and anxiety-like behaviour in rats

“…Rats typically produce calls at a 50kHz frequency (true range: 30-90kHz) and shorter call rate in pleasant situations, and longer calls in a 22kHz frequency (true range: 18-30kHz) in aversive situations (Saito et al, 2019). Previous literature has shown that 50kHz USVs are elicited when rats are exposed to cues that predict rewarding stimuli such as food or drugs of abuse (Buck et al, 2014).…”