Ultrasonic Vocalizations Acoustics Research Articles

Changes in ultrasonic vocalizations after unilateral cerebral ischemia in a rat stroke model

Stroke frequently results in communication impairments that negatively impact quality of life and overall recovery, yet the biological mechanisms underlying these changes are not well understood. Ultrasonic vocalizations (USVs) in rodent models of disease and aging have been used to improve our understanding of the biological mechanisms that underlie vocal deficits and their response to interventions. Changes in USVs after middle cerebral artery occlusion (MCAO) in mice have been reported, yet rat models have significant anatomical and behavioral advantages over mice, including the ability to vocally train rats with an established paradigm. We sought to determine whether a unilateral MCAO rat stroke model provides a biologically and behaviorally relevant way to study post stroke vocalization deficits. We hypothesized that left MCAO would be associated with changes in USVs. Six weeks after MCAO or sham-control surgery, USVs were recorded in rats using an established mating paradigm. Stroke was associated with differences in USV acoustics including more frequent use of simple calls characterized by shorter durations and restricted bandwidths. These parameters were also found to correlate with post stroke lingual weakness. This is the first study to describe changes to rat USVs using a stroke model. These results suggest the unilateral MCAO rat stroke model is a biologically and behaviorally relevant model to understand how stroke affects vocal behaviors.

Biological and Acoustic Sex Differences in Rat Ultrasonic Vocalization.

The rat model is a useful tool for understanding peripheral and central mechanisms of laryngeal biology. Rats produce ultrasonic vocalizations (USVs) that have communicative intent and are altered by experimental conditions such as social environment, stress, diet, drugs, age, and neurological diseases, validating the rat model’s utility for studying communication and related deficits. Sex differences are apparent in both the rat larynx and USV acoustics and are differentially affected by experimental conditions. Therefore, the purpose of this review paper is to highlight the known sex differences in rat USV production, acoustics, and laryngeal biology detailed in the literature across the lifespan.

The effects of the estrous cycle, menopause, and recording condition on female rat ultrasonic vocalizations

The goal of this study was to evaluate the effects of ovarian hormones on female rat ultrasonic vocalizations (USVs). Twenty (10 control and 10 ovariectomized) 3-month-old female rats were recorded in 3 recording conditions (elicitation, dyad, and isolation) over a full estrous cycle or time-matched duration. There were differences in USV acoustics (frequency and complexity parameters) across recording conditions but no differences in USV acoustics between control and ovariectomized groups. USVs produced in isolation had lower frequency and complexity parameters than elicited USVs for both control and ovariectomized rats. Additionally, for control rats, USV parameters of frequency, complexity, duration, and intensity changed depending on the estrous state. Therefore, although fluctuating hormone levels may influence USV acoustics, this variation can be controlled for by ovariectomizing female rats.

Laryngeal Neuromuscular Response to Short- and Long-Term Vocalization Training in Young Male Rats.

Purpose Although vocal training is often purported to restore and rebalance laryngeal muscle function, little is known about the direct effects of vocal training on the laryngeal muscles themselves. Consequently, parameters of vocal exercise dose, such as training duration and intensity, have not been well defined. The goal of this study was to use a behavioral animal model to determine the effects of short- and long-term ultrasonic vocalization (USV) training on USV acoustics, thyroarytenoid (TA) muscle neuromuscular junctions (NMJs), and TA muscle fiber size in adult rats. Method Twenty-four young adult male Long-Evans rats were divided into 3 groups (untrained control, 4-week training, and 8-week training). Baseline and posttraining USVs were recorded and acoustically analyzed for fundamental frequency, frequency bandwidth, amplitude, and duration. Presynaptic and postsynaptic NMJ morphological features and muscle fiber size were measured in the TA. Results USV training had no effect on USV acoustics. Eight weeks of USV training, however, resulted in a lower NMJ motor endplate dispersion ratio, consistent with previous findings. USV training did not affect fiber size within the TA muscle. Conclusions This study demonstrated that 8 weeks of USV training can induce peripheral neural adaptations in the NMJ of the TA muscle in young rats. The observed adaptations suggest that vocal training is consistent with endurance-type exercise, but the adaptations occur on a longer time scale than similar adaptations in the limb muscles.

Social isolation alters ultrasonic vocalizations but not thyroarytenoid neuromuscular junctions in old rats.

Age-related muscle atrophy of the laryngeal muscles contributes to presbyphonia. Remodeling of the neuromuscular junction is one aspect underlying age-related muscle atrophy. Although muscle disuse has been shown to exacerbate age-related neuromuscular changes in the limb muscles, it is unknown if reduced vocal use has a similar effect in the laryngeal muscles. The objective of this study was to examine the use of social isolation as a novel method to reduce vocal use in old rats-and the impact of that reduced vocal use on ultrasonic vocalization acoustics and neuromuscular junction morphology in the thyroarytenoid muscle. Animal group comparison. Old F344/BN rats (31 months of age) were socially isolated (n = 8) or communally housed (n = 8) for 8 weeks. Effect of housing condition on ultrasonic vocalization acoustics was assessed by calculating the changes in vocalization fundamental frequency and amplitude from baseline to 8 weeks. Neuromuscular junction morphology was measured in the lateral and medial portions of the thyroarytenoid muscle at the conclusion of the experiment. Vocalization amplitude decreased by a mean of -4.4 dB (standard deviation [SD], 4.49) after social isolation, whereas amplitude increased by a mean of 5.7 dB (SD, 5.07) in the communally housed rats (P = 0.002). There was no significant difference in the change in fundamental frequency between groups. Furthermore, there were no group differences in any measure of neuromuscular junction morphology. These results suggest that neuromuscular junctions in the thyroarytenoid muscle of old rats are unaffected by 8 weeks of social isolation, despite functional changes in vocalizations. NA Laryngoscope, 129:E9-E14, 2019.

Dopamine D1 and D2 receptor antagonism effects on rat ultrasonic vocalizations

Voice disorders manifest in the early stages of Parkinson disease (PD), suggesting the vulnerability of the laryngeal sensorimotor system to mild alterations in dopamine signaling. Previous research has demonstrated that manipulations of central dopamine result in acoustic changes in rat ultrasonic vocalization (USV) and selective manipulation of receptor subtypes results in dose dependent changes in call rate and complexity. However, no study has specifically focused on the influence of dopamine receptor subtypes on acoustic features of USV production. This study examined the influence of D1 and D2 receptor subtypes on voluntary laryngeal sensorimotor control (USV) and gross whole-body involvement. Rat USV acoustics and catalepsy descent time were analyzed following the administration of selective D1 and D2 receptor antagonists in isolation and in combination, and a vehicle control. Results support the hypothesis that degradations of the acoustic signal would be most severe following combined receptor antagonism (D1+D2) compared with D1 or D2 receptor antagonism alone, and the vehicle (saline) condition. In addition, results indicate that selective D1 receptor antagonism alters acoustic parameters to a greater extent than D2 receptor antagonism. Thus, dopamine receptor subtypes appear to influence acoustic parameters to different degrees. Catalepsy descent time was longest following combined dopamine receptor antagonism but was also significantly increased with selective D1 or D2 antagonism. Together, these results support the potentially different contributions receptor subtypes play in cranial and limb sensorimotor control.

Vocal Training Mitigates Age-Related Changes Within the Vocal Mechanism in Old Rats

Aging affects voice production and is associated with reduced communicative ability and quality of life. Voice therapy is a critical component of treatment, but its effects on neuromuscular mechanisms are unknown. The ultrasonic vocalizations (USVs) of rats can be used to test the effects of aging and voice use on the laryngeal neuromuscular system. This study tested the hypothesis that age-related changes in the USVs of rats and laryngeal neuromuscular junctions can be reversed through vocal exercise. Young and old rats were trained for 8 weeks to increase their USVs and were compared with a no intervention group pre- and post-treatment. USV acoustics and aspects of neuromuscular junction (NMJ) morphology were measured in the thyroarytenoid muscle. Vocal training reduced or eliminated some age differences found in both USVs and NMJs. We conclude that vocal exercise may assist in mitigating age-related changes in voice characteristics and underlying neuromuscular adaptations.