Faculty Bibliography

OBJECTIVE: The human voice is sexually dimorphic in obvious ways, such as differences in fundamental frequency and gross laryngeal anatomy, but also in less apparent ways, such as in the prevalence and types of voice disorders and the manifestation of voice changes in advanced age. Differences between males and females are rarely explored, however, in mechanistic animal studies. The goal of this study was to explore sexual dimorphism in laryngeal function and structure in adult rats by examining ultrasonic vocalization acoustics and muscle fiber size and type in the thyroarytenoid muscle. STUDY DESIGN: Animal group comparison. METHODS: Spontaneous ultrasonic vocalizations from 10 male adult rats and 10 female adult rats were recorded, classified, and acoustically analyzed. Cross-sections of the thyroarytenoid muscle were stained and imaged for analysis of muscle fiber size and type. Acoustic and muscle parameters were statistically compared between sexes. RESULTS: Male rats had a lower mean frequency of short ultrasonic vocalizations. Male rats also had a larger mean fiber size in the external division of the thyroarytenoid and larger overall muscle area in both the vocalis and external divisions of the thyroarytenoid. However, muscle fiber type compositions were similar between sexes in both the vocalis and external division of the thyroarytenoid muscles. CONCLUSION: Functional and structural laryngeal differences exist between adult male and female rats; therefore, the rat model can be used to further study sexual dimorphism of the voice. LEVEL OF EVIDENCE: NA. Laryngoscope, 2017.

Ultrasonic vocalizations are a useful tool for inferring affective states in the rat and have been incorporated in research paradigms modeling important human conditions. While the majority of studies report the quantity or rate of observed ultrasonic vocalizations, growing evidence suggests that critical data may be contained in the acoustic features of individual vocalizations. Thus, the goal of the present study was to develop and validate a method for measuring acoustic parameters of ultrasonic vocalizations that were collected using automatic template detection. Acoustic parameters derived using this method were found to be comparable to those collected using commercially available software.

OBJECTIVES/HYPOTHESIS: The primary objectives of this study were to determine the intrasubject reliability of repeated measures of maximum phonation time (MPT) duration during a single session and to examine the effects of age, sex, and total phonatory airflow on this reliability. STUDY DESIGN: This study used repeated measures. METHODS: Duration and total phonatory airflow during three consecutive MPT trials were collected from 20 participants evenly distributed between age (young/old) and sex (male/female) groups. Intraclass correlation coefficient and repeated-measures analysis of variance were used to examine the reliability of MPT across trials and to test for possible effects of age and sex. RESULTS: Intraclass correlation for MPT duration was strong across all participants (0.86), but MPT duration was not stable across trials (F2, 32 = 3.58, P = 0.04), with the second trial having the longest duration on average (P = 0.03). There was no effect of trial on total phonatory airflow (F2, 32 = 1.08, P = 0.35). The relationship between MPT duration and total phonatory airflow, however, did not remain consistent across trials (F2, 31 = 3.58, P = 0.04). There were no effects of age or sex on any variables. CONCLUSIONS: The variability in MPT duration across trials and the inconsistent relationship between MPT duration and total phonatory airflow indicate that there is variability in laryngeal efficiency across repeated MPT trials. Therefore, the results of this study corroborate previous research supporting the assertion that MPT is not a reliable measure of laryngeal aerodynamics.

Fragile X Syndrome (FXS) is the leading form of inherited intellectual disability. It is caused by the transcriptional silencing of FMR1, the gene which codes for the Fragile X Mental Retardation Protein (FMRP). Patients who have FXS exhibit numerous behavioral and cognitive impairments, such as attention-deficit/hyperactivity disorder, obsessive compulsive disorder, and autistic-like behaviors. In addition to these behavioral abnormalities, FXS patients have also been shown to exhibit various deficits in communication such as abnormal sentence structures, increased utterances, repetition of sounds and words, and reduced articulation. These deficits can dramatically hinder communication for FXS patients, exacerbating learning and cognition impairments while decreasing their quality of life. To examine the biological underpinnings of these communication abnormalities, studies have used a mouse model of the Fragile X Syndrome; however, these vocalization studies have resulted in inconsistent findings that often do not correlate with abnormalities observed in FXS patients. Interestingly, a detailed examination of frequency modulated vocalizations that are believed to be a better assessment of rodent communication has never been conducted. The following study used courtship separation to conduct a detailed examination of frequency modulated ultrasonic vocalizations (USV) in FXS mice. Our analyses of frequency modulated USVs demonstrated that adult FXS mice exhibited longer phrases and more motifs. Phrases are vocalizations consisting of multiple frequency modulated ultrasonic vocalizations, while motifs are repeated frequency modulated USV patterns. Fragile X mice had a higher proportion of "u" syllables in all USVs and phrases while their wildtype counterparts preferred isolated "h" syllables. Although the specific importance of these syllables towards communication deficits still needs to be evaluated, these findings in production of USVs are consistent with the repetitive and perseverative speech patterns observed in FXS patients. This study demonstrates that FXS mice can be used to study the underlying biological mechanism(s) mediating FXS vocalization abnormalities.

Many individuals with Parkinson disease (PD) have difficulty producing normal speech and voice, resulting in problems with interpersonal communication and reduced quality of life. Translational animal models of communicative dysfunction have been developed to assess disease pathology. However, it is unknown whether acoustic feature changes associated with vocal production deficits in these animal models lead to compromised communication. In rodents, male ultrasonic vocalizations (USVs) have a well-established role in functional inter-sexual communication. To test whether acoustic deficits in USVs observed in a PTEN-induced putative kinase 1 (PINK1) knockout (KO) PD rat model compromise communication, we presented recordings of male PINK1 KO USVs and normal wild-type (WT) USVs to female rat listeners. We measured approached behavior and immediate early gene expression (c-Fos) in brain regions implicated in auditory processing and sexual motivation. Our results suggest that females show reduced approach in response to PINK1 KO USVs compared with WT. Moreover, females exposed to PINK1 KO USVs had lower c-Fos immunolabeling in the nucleus accumbens, a region implicated in sexual motivation. These results are the first to demonstrate that vocalization deficits in a rat PD model result in compromised communication. Thus, the PINK1 KO PD model may be valuable for assessing treatments aimed at restoring vocal communicative function.

Vocal communication is negatively affected by neurodegenerative diseases, such as Parkinson disease, and by aging. The neurological and sensorimotor mechanisms underlying voice deficits in Parkinson disease and aging are not well-understood. Rat ultrasonic vocalizations provide a unique behavioral model for studying communication deficits and the mechanisms underlying these deficits in these conditions. The purpose of this review was to examine the existing literature for methods using rat ultrasonic vocalization with regard to the primary disease pathology of Parkinson disease, dopamine denervation, and aging. Although only a small amount of papers were found for each of these topics, results suggest that both shared and unique acoustic deficits in ultrasonic vocalizations exist across conditions and that these acoustic deficits are due to changes in either dopamine signaling or denervation and in aging models changes to the nucleus ambiguus, at the level of the neuromuscular junction, and the composition of the vocal folds in the larynx. We conclude that ultrasonic vocalizations are a useful tool for studying biologic mechanisms underlying vocal communication deficits in neurodegenerative diseases and aging.

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.

OBJECTIVES/HYPOTHESIS: Singing-voice classification is often considered the cornerstone of a classical singer's identity. Traditionally, classification has been a highly subjective, nonstandardized process. As a result, misclassification of the singing voice is thought to be common, especially in young singers. Long-term average spectrum (LTAS) average is an objective measurement that could be used to classify a singer's voice. The purpose of this study was to determine the relationship of LTAS with singing-voice classification. STUDY DESIGN: Descriptive between-subject study. METHODS: Nine professional classical male singers performed the "Star Spangled Banner" in a comfortable key of their choice. LTAS was calculated for the first two phrases, the remainder of the song, and the entire song. The overall LTAS averages of each sample as well as the physiological and singing ranges were compared with self-reported singing-voice classification. RESULTS: Voice classification and overall LTAS average were moderately correlated, but the strength of the correlation varied with each sample. The strongest correlation was with the entire song. Voice classification and singing range were strongly correlated. CONCLUSIONS: LTAS remains a promising tool to aid in singing-voice classification. However, how to best use LTAS in classification remains unclear because of the influence of sample length and phonetic and pitch content on LTAS.