Vocal Production Research Articles

Ultrasound and ultraviolet: crypsis in gliding mammals.

Gliding is only present in six extant groups of mammals-interestingly, despite divergent evolutionary histories, all mammalian gliders are strictly nocturnal. Gliding mammals also seem to have relatively high rates of ultrasound use and ultraviolet-induced photoluminescence (UVP) in contrast with their close relatives. Therefore, we hypothesized that, despite diverging lineages, gliding mammals use similar modes of cryptic communication compared to their non-gliding counterparts. We developed two datasets containing the vocal range (minimum-maximum of the dominant harmonic; kHz) and UVP of 73 and 82 species, respectively; we report four novel vocal repertoires and 57 novel observations of the presence or absence of UVP. We complemented these datasets with information about body size, diel activity patterns, habitat openness, and sociality to explore possible covariates related to vocal production and UVP. We found that the maximum of the dominant harmonic was significant higher in gliding mammals when vocalizing than their non-gliding relatives. Additionally, we found that nocturnality was the only significant predictor of UVP, consistent with the previous hypothesis that luminophores primarily drive UVP in mammal fur. In contrast, however, we did not find UVP ubiquitous in nocturnal mammals, suggesting that some unknown process may contribute to variation in this trait.

Brainstem control of vocalization and its coordination with respiration.

Phonation critically depends on precise controls of laryngeal muscles in coordination with ongoing respiration. However, the neural mechanisms governing these processes remain unclear. We identified excitatory vocalization-specific laryngeal premotor neurons located in the retroambiguus nucleus (RAmVOC) in adult mice as being both necessary and sufficient for driving vocal cord closure and eliciting mouse ultrasonic vocalizations (USVs). The duration of RAmVOC activation can determine the lengths of both USV syllables and concurrent expiration periods, with the impact of RAmVOC activation depending on respiration phases. RAmVOC neurons receive inhibition from the preBötzinger complex, and inspiration needs override RAmVOC-mediated vocal cord closure. Ablating inhibitory synapses in RAmVOC neurons compromised this inspiration gating of laryngeal adduction, resulting in discoordination of vocalization with respiration. Our study reveals the circuits for vocal production and vocal-respiratory coordination.

Infant vocal productions coincide with body movements.

Producing recognizable words is a difficult motor task; a one-syllable word can require the coordination of over 80 muscles. Thus, it is not surprising that the development of word productions in infancy lags considerably behind receptive language and is a known limiting factor in language development. A large literature has focused on the vocal apparatus, its articulators, and language development. There has been limited study of the relations between non-speech motor skills and the quality of early speech productions. Here we present evidence that the spontaneous vocalizations of 9- to 24-month-old infants recruit extraneous, synergistic co-activations of hand and head movements and that the temporal precision of the co-activation of vocal and extraneous muscle groups tightens with age and improved recognizability of speech. These results implicate an interaction between the muscle groups that produce speech and other body movements and provide new empirical pathways for understanding the role of motor development in language acquisition. RESEARCH HIGHLIGHTS: The spontaneous vocalizations of 9- to 24-month-old infants recruit extraneous, synergistic co-activations of hand and head movements. The temporal precision of these hand and head movements during vocal production tighten with age and improved speech recognition. These results implicate an interaction between the muscle groups producing speech with other body movements. These results provide new empirical pathways for understanding the role of motor development in language acquisition.

Factors influencing the minimum audible change in head orientation of a talker

Humans can detect changes in the head orientation (a.k.a. facing angle) of a talker using only auditory cues. Head orientation cues are beneficial for determining whether one is the intended recipient of an utterance and for segregating a target talker from background talkers. Because human talkers are directional sound sources, binaural cues and monoaural spectral cues can both contribute to talker head orientation perception. In this study, we assessed listeners’ sensitivity to talker head orientation changes using only monaural cues. We tested several factors that could influence the minimum audible change in head orientation: talker and gender (two male, two female), stimulus bandwidth (full-band versus low-pass filtered at 8 or 10 kHz), transducer (loudspeaker versus headphone), stimulus uncertainty (interleaved versus blocked presentation of four talkers), and vocal production mode (speech versus singing). Bandlimiting at 8 or 10 kHz led to worse performance, as did increasing stimulus uncertainty. The effect of transducer was very limited. Performance with speech was better than that with singing. The effect of talker was large and consistent, suggesting individual variability in speech directivity patterns may affect head orientation cues. [Work supported by NIH grant R01DC019745.]

Vocal learning-associated convergent evolution in mammalian proteins and regulatory elements.

Vocal production learning ("vocal learning") is a convergently evolved trait in vertebrates. To identify brain genomic elements associated with mammalian vocal learning, we integrated genomic, anatomical, and neurophysiological data from the Egyptian fruit bat (Rousettus aegyptiacus) with analyses of the genomes of 215 placental mammals. First, we identified a set of proteins evolving more slowly in vocal learners. Then, we discovered a vocal motor cortical region in the Egyptian fruit bat, an emergent vocal learner, and leveraged that knowledge to identify active cis-regulatory elements in the motor cortex of vocal learners. Machine learning methods applied to motor cortex open chromatin revealed 50 enhancers robustly associated with vocal learning whose activity tended to be lower in vocal learners. Our research implicates convergent losses of motor cortex regulatory elements in mammalian vocal learning evolution.

The everyday speech environments of preschoolers with and without cochlear implants.

Children who receive cochlear implants develop spoken language on a protracted timescale. The home environment facilitates speech-language development, yet it is relatively unknown how the environment differs between children with cochlear implants and typical hearing. We matched eighteen preschoolers with implants (31-65 months) to two groups of children with typical hearing: by chronological age and hearing age. Each child completed a long-form, naturalistic audio recording of their home environment (appx. 16 hours/child; >730 hours of observation) to measure adult speech input, child vocal productivity, and caregiver-child interaction. Results showed that children with cochlear implants and typical hearing were exposed to and engaged in similar amounts of spoken language with caregivers. However, the home environment did not reflect developmental stages as closely for children with implants, or predict their speech outcomes as strongly. Home-based speech-language interventions should focus on the unique input-outcome relationships for this group of children with hearing loss.

Central Autonomic Mechanisms Involved in the Control of Laryngeal Activity and Vocalization.

In humans, speech is a complex process that requires the coordinated involvement of various components of the phonatory system, which are monitored by the central nervous system. The larynx in particular plays a crucial role, as it enables the vocal folds to meet and converts the exhaled air from our lungs into audible sounds. Voice production requires precise and sustained exhalation, which generates an air pressure/flow that creates the pressure in the glottis required for voice production. Voluntary vocal production begins in the laryngeal motor cortex (LMC), a structure found in all mammals, although the specific location in the cortex varies in humans. The LMC interfaces with various structures of the central autonomic network associated with cardiorespiratory regulation to allow the perfect coordination between breathing and vocalization. The main subcortical structure involved in this relationship is the mesencephalic periaqueductal grey matter (PAG). The PAG is the perfect link to the autonomic pontomedullary structures such as the parabrachial complex (PBc), the Kölliker-Fuse nucleus (KF), the nucleus tractus solitarius (NTS), and the nucleus retroambiguus (nRA), which modulate cardiovascular autonomic function activity in the vasomotor centers and respiratory activity at the level of the generators of the laryngeal-respiratory motor patterns that are essential for vocalization. These cores of autonomic structures are not only involved in the generation and modulation of cardiorespiratory responses to various stressors but also help to shape the cardiorespiratory motor patterns that are important for vocal production. Clinical studies show increased activity in the central circuits responsible for vocalization in certain speech disorders, such as spasmodic dysphonia because of laryngeal dystonia.

Fine-Tuning of a Voice Production Model to Estimate Impact Stress Using a Metaheuristic Method

Introduction. In vocal production models employing spring-mass-damper frameworks, precision in determining damping coefficients that align with physiological vocal fold characteristics is crucial, accounting for potential variations in the representation of viscosity-elasticity properties. Objective. This study aims to conduct a parametric fitting of a vocal production model based on a mass-spring-damper system incorporating subglottic pressure interaction, with the purpose of accurately modeling the collision forces exerted by vocal folds during phonation. Method. A metaheuristic search algorithm was employed for parametric synthesis. The algorithm was applied to elasticity coefficients c1 and c2, as well as damping coefficients ε1 and ε2, which directly correlate with the mass matrices of the model. This facilitates the adjustment of fold composition to achieve desired physiological behavior. Results. The vocal system's behavior for each simulation cycle was compared to a predefined standard under normal conditions. The algorithm determined the simulation endpoint by evaluating discrepancies between key features of the obtained signals and the desired ones. Conclusion. Parametric fitting enabled the approximation of physiological vocal production behavior, providing estimates of the impact forces experienced by vocal folds during phonation.

Midbrain neurons important for the production of mouse ultrasonic vocalizations are not required for distress calls

A fundamental feature of vocal communication is that animals produce vocalizations with different acoustic features in different behavioral contexts (contact calls, territorial calls, courtship calls, etc.). The midbrain periaqueductal gray (PAG) is a key region that regulates vocal production, and artificial activation of the PAG can elicit the production of multiple species-typical vocalization types.1,2,3,4,5,6,7,8,9 How PAG circuits are organized to regulate the production of different vocalization types remains unknown. On the one hand, studies have found that partial PAG lesions abolish the production of some vocalization types while leaving others intact,3,8,10,11 suggesting that different populations of PAG neurons might control the production of different vocalization types. On the other hand, electrophysiological recordings have revealed individual PAG neurons that increase their activity during the production of multiple vocalization types,12,13,14 suggesting that some PAG neurons may regulate the production of more than one vocalization type. To test whether a single population of midbrain neurons regulates the production of different vocalization types, we applied intersectional methods to selectively ablate a population of midbrain neurons important for the production of ultrasonic vocalizations (USVs) in mice. We find that, although ablation of these PAG-USV neurons blocks USV production in both males and females, these neurons are not required for the production of distress calls. Our findings suggest that distinct populations of midbrain neurons control the production of different vocalization types.

Temporal scaling of motor cortical dynamics reveals hierarchical control of vocal production.

Neocortical activity is thought to mediate voluntary control over vocal production, but the underlying neural mechanisms remain unclear. In a highly vocal rodent, the male Alston's singing mouse, we investigate neural dynamics in the orofacial motor cortex (OMC), a structure critical for vocal behavior. We first describe neural activity that is modulated by component notes (~100 ms), probably representing sensory feedback. At longer timescales, however, OMC neurons exhibit diverse and often persistent premotor firing patterns that stretch or compress with song duration (~10 s). Using computational modeling, we demonstrate that such temporal scaling, acting through downstream motor production circuits, can enable vocal flexibility. These results provide a framework for studying hierarchical control circuits, a common design principle across many natural and artificial systems.

Predicting pointing from early socioemotional communication with mothers, fathers, and strangers through the lens of temperamental reactivity.

Socioemotional and referential communication are primary expressions of interpersonal engagement in infancy and beyond. Early socioemotional communication in dyadic interactions may form a foundation for triadic referential communication and gesture production, yet the role of temperament in moderating their association has not been examined. We investigated whether early socioemotional communication behaviors, and infant temperamental reactivity, were associated with later pointing production. Participants were 51 infants (45% girls) and both their parents (86.5% Dutch). Early infant socioemotional communication (production of smile, vocalizations, and gaze) was observed during separate home-based face-to-face interactions with mothers, fathers, and strangers at 4 and 8 months. At both ages, mothers and fathers reported on infant temperamental surgency and negative affectivity, and overall means were calculated. Referential communication (declarative pointing) was measured during structured lab-based observations at 12 and 15 months. Socioemotional and referential communication behaviors were microanalytically coded second by second. Poisson multilevel regression analyses indicated interaction effects between temperament and smile, vocalizations, and gazes to the adult's face with each partner in predicting pointing. High levels of infant temperamental surgency tended to enhance positive associations between early socioemotional communication behaviors with mothers and fathers and pointing. By contrast, high levels of negative affectivity tended to dampen associations between early communication behaviors with strangers and pointing. Results highlight the importance of infant socioemotional communication with diverse partners and the moderating role of temperamental reactivity in predicting referential communication. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Sleep fragmentation disrupts vocal interactions in rats

ABSTRACT Repeated interruption of the sleep cycle, commonly known as sleep fragmentation, is associated with a plethora of health issues, ranging from mood swings and memory loss to severe neurodegenerative disorders. Despite being a significant health problem with consequences on the social lives of individuals, its effect on vocal communication has been poorly studied. Here we show that sleep fragmentation induces a decrease in vocal production of a social rodent, without altering the acoustic characteristics of the vocalisations emitted. We conducted an experimental study using Rattus norvegicus rats, known for their ultrasonic vocal repertoire, in which we frequently woke pairs of individuals during their daily sleeping period. The rats whose sleep was artificially fragmented produced fewer vocalisations during their active periods than control pairs whose sleep was not disturbed. This decrease in vocal activity occurred after only two phases of fragmented sleep and was maintained throughout the 4 weeks of the experimentation. Conversely, sleep fragmentation had no effect on the rats’ vocal repertoire. Our results demonstrate that fragmented sleep impacts vocal interactions and emotional expression in a social mammal, and that this effect is maintained over weeks without recovering.

Breathing with the Conductor? A Prospective, Quasi-Experimental Exploration of Breathing Habits in Choral Singers.

The breathing technique is a determining factor for the sound quality of the singers' vocal production and thus crucial for the choral sound. The aim of this study was to examine choral singers' awareness of breathing techniques and habits while singing and to identify potential correlations between the breathing technique and the preparatory gestures of the conductor. In our prospective, quasi-experimental study, 720 choral singers answered a 25-item anonymous online survey which focused on demographic information, musical and choral experience, information on choir (size, type, repertoire) and conductor (age, gender, level of expertise). As the central issue we examined the subjects' general knowledge of breathing techniques and habits and their own use thereof in choral practice. Finally, subjects were asked to watch videos showing two different preparatory conducting gestures and to assess the meaning of these gestures. The results of the study show that the majority of choral singers (68.1%) inhale not before and not after, but during the conductor's preparatory gesture. The most well-known (94.7%) and allegedly most frequently (81.8%) used type of inhalation is abdominal breathing. Six times more singers associate abdominal breathing with an outward gesture rather than with the more frequently occurring inward-upward gesture. The conducting literature does not discriminate between out- and inward preparatory gestures and describe them as equivalent. However, according to our data, a vast majority of singers assign these gestures to different types of inhalation which influences singing technique and sound quality. This might lead to ambiguous action-reaction expectations from singers and conductors in rehearsals and concerts.

Spontaneous Production Rates in Song and Speech

Many everyday tasks appear to be performed at an optimal rate that differs between individuals but is consistent within individuals. These optimal rates are estimated using a participant's Spontaneous Production Rate (SPR), the rate at which an individual produces sequences of sounds in the absence of external tempo cues. A previous study that measured SPRs in speech and piano production found no association between SPRs across tasks, a result suggesting that domain-specific constraints determine optimal rates. The present study addressed whether this dissociation would remain when music and speech are produced with the same effector system: vocal production. Participants spoke short, well-known phrases and sang familiar children's songs on “da” to avoid memorization of words. SPRs were measured by the mean inter-onset interval (IOI) between successively produced syllables or tones and showed large individual differences. Results showed consistent SPRs within individuals within each domain (speaking or singing) as well as consistent SPRs across the speaking and singing conditions. These results align with theories of optimal rates based on energy efficiency arising from biomechanical constraints rather than domain-specific communication goals.

Vocal Self-Perception of Singers During COVID-19 Pandemic.

to compare the self-perception of vocal fatigue and use of singing voice during the COVID-19 pandemic between professional and amateur singers and to relate this self-perception with vocal use characteristics during this period. Participants were 121 singers divided into professional singers group (PSG) (12 men and 20 women) comprising singers who depended exclusively on singing as a profession and an amateur singers group (ASG) (37 men and 52 women) of singers who did not depend exclusively on singing for their livelihood. All answered online questionnaires through Google Forms ®. Sociodemographic and vocal characteristics were investigated before and during the pandemic; symptoms of vocal fatigue were assessed through the vocal fatigue index (VFI); and self-perception of use of singing voice through the evaluation of the ability to sing easily protocol for Brazil (EASE-Br). In the comparison between groups, the PSG presented higher scores of vocal fatigue in fatigue and vocal limitation (P=0.045), vocal restriction (P=0.002), and recovery with vocal rest (P=0.008) domains than did the ASG. There was no difference between the groups regarding the use of singing voice. Based on the relationship between self-perception and vocal use characteristics during the pandemic, it was observed that the presence of vocal complaint was the only factor associated with self-perception of fatigue symptomatology in both groups. Regarding the self-perception of the current status of the singing voice, singing time, the presence of vocal complaints, the need to increase visual concentration, and the perception of vocal worsening during the pandemic were considered predictive for amateur singers. For professional singers, vocal complaints and vocal training were predictors for self-perception of the current status of the singing voice. Professional singers presented with higher scores of vocal fatigue than did amateur singers. The symptomatology of vocal fatigue was associated with the presence of vocal complaints in both groups. However, self-perception of the current status of the singing voice was different between the groups and was associated with vocal training for professional singers and characteristics of vocal demand of singing voice during the pandemic period for amateur singers.

Voice and Temporal Auditory Processing in Elderly People: A Correlation Study.

Introduction The voice and hearing can be affected to different degrees by aging, which can cause communication difficulties for elderly people. Vocal production requires effective temporal auditory processing at central levels within the nervous system, which can be compromised by the aging process. Objective To analyze the correlation between voice and temporal auditory processing in older adults. Materials and Methods A total of 40 elderly people aged 60 years or older were subdivided into 2 groups according to the presence or absence of vocal symptoms measured by the Voice Symptom Scale. All of the participants were submitted to auditory temporal tests, vocal self-assessment, and acoustic and perceptual auditory analyses of voice. Results Most of the subjects assessed had decreased voice intensity and normal variability in terms of vocal quality. The performance was normal in the Pitch Pattern Sequence test and altered in the Random Gap Detection test. In the Masking Period Pattern test, the detection thresholds for the target signal were increased in the presence of masking in different temporal target signal positions. Only pitch differed between the two groups. There were differences between the genders regarding frequency, shimmer, the overall severity of the alteration, and roughness. There was a correlation regarding temporal resolution ability and the overall severity of the alteration and roughness of the voice. Conclusion There is a central auditory impairment in temporal resolution which is correlated with vocal alterations in the elderly.

A neural circuit for vocal production responds to viscerosensory input in the songbird.

Motor performance is monitored continuously by specialized brain circuits and used adaptively to modify behavior on a moment-to-moment basis and over longer time periods. During vocal behaviors, such as singing in songbirds, internal evaluation of motor performance relies on sensory input from the auditory and vocal-respiratory systems. Sensory input from the auditory system to the motor system, often referred to as auditory feedback, has been well studied in singing zebra finches (Taeniopygia guttata), but little is known about how and where nonauditory sensory feedback is evaluated. Here we show that brief perturbations in air sac pressure cause short-latency neural responses in the higher-order song control nucleus HVC (used as proper name), an area necessary for song learning and song production. Air sacs were briefly pressurized through a cannula in anesthetized or sedated adult male zebra finches, and neural responses were recorded in both nucleus parambigualis (PAm), a brainstem inspiratory center, and HVC, a cortical premotor nucleus. These findings show that song control nuclei in the avian song system are sensitive to perturbations directly targeted to vocal-respiratory, or viscerosensory, afferents and support a role for multimodal sensory feedback integration in modifying and controlling vocal control circuits.NEW & NOTEWORTHY This study presents the first evidence of sensory input from the vocal-respiratory periphery directly activating neurons in a motor circuit for vocal production in songbirds. It was previously thought that this circuit relies exclusively on sensory input from the auditory system, but we provide groundbreaking evidence for nonauditory sensory input reaching the higher-order premotor nucleus HVC, expanding our understanding of what sensory feedback may be available for vocal control.

Ostrich (Struthio camelus) syrinx morphology and vocal repertoire across postnatal ontogeny and sex: Implications for understanding vocal evolution in birds.

Vocal production in birds has been the target of considerable research that mostly has focused on phylogenetically well-nested songbirds. Anatomical descriptions and recordings of many non-songbirds have often only focused on a single ontogenetic stage or sex. While basic morphology of the vocal organ (syrinx) of ostrich (Palaeognathae, Struthio camelus) has been known since the 1800s, descriptions of its vocal repertoire and syrinx anatomy since then have been incomplete or inconsistent. New toolkits now enable detailed qualitative description of internal anatomy and meristic data and allow it to be compared to vocal production. Here we describe the anatomy of the syrinx in Struthio camelus for three post-hatching ontogenetic stages and both an adult male and female utilizing dissection and contrast enhanced X-ray computed tomography (diceCT). We find changes in ring geometry and spacing through ontogeny as well as lateral labia thickness. We document a small unpaired, midline, cartilaginous structure, a "pessuliform process" at the tracheobronchial juncture present throughout ontogeny and in both males and females. Investigation of the vocal repertoire of ostriches across ontogeny using a new dataset of 77 recordings led to identification of four vocalizations not previously reported in the literature, including the simultaneous production of a hiss and tonal. We find syrinx morphology largely consistent across ontogeny and in male and female adults. Both are capable of producing long duration tonal calls, but these may be more frequent in male birds. Closed-mouth boom calls remain unique to males. A detailed understanding of diversity in parts of early diverging clades is pivotal in attempting to estimate features of the ancestral syrinx in birds and how avian vocalization evolved.

Study of repertoire use reveals unexpected context-dependent vocalizations in bottlenose dolphins (Tursiops truncatus).

Dolphins are known for their complex vocal communication, not least because of their capacity for acoustic plasticity. Paradoxically, we know little about their capacity for flexible vocal use. The difficulty in describing the behaviours performed underwater while vocalizing makes it difficult to analyse the contexts of emissions. Dolphins' main vocal categories are typically considered to be used for scanning the environment (clicks), agonistic encounters (burst pulses) and socio-affiliative interactions (whistles). Dolphins can also combine these categories in mixed vocal emissions, whose use remains unclear. To better understand how vocalizations are used, we simultaneously recorded vocal production and the associated behaviours by conducting underwater observations (N = 479 events) on a group of 7 bottlenose dolphins under human care. Our results showed a non-random association between vocal categories and behavioural contexts. Precisely, clicks were preferentially emitted during affiliative interactions and not during other social/solitary contexts, supporting a possible complementary communicative function. Burst pulses were associated to high arousal contexts (agonistic and social play), pinpointing on their use as an "emotively charged" signal. Whistles were related to solitary swimming and not preferentially produced in any social context. This questions whistles' functions and supports their potential role as a distant contact call. Finally, mixed vocalizations were especially found associated with sexual (bust pulse-whistle-click), solitary play (burst pulse-whistle) and affiliative (click-whistle) behaviours. Depending on the case, their emission seems to confirm, modify or refine the functions of their simple counterparts. These results open up new avenues of research into the contextual use of dolphin acoustic signals.

Daily Speaking Time and Voice Intensity before and after Hearing Aid Rehabilitation in Adult Patients with Hearing Loss

Introduction: Hearing loss (HL) strongly impacts communication abilities and impairs social interactions. Moreover, it modifies the vocal parameters of affected patients. The effects of hearing rehabilitation through hearing aids (HA) on the vocal production of patients suffering from HL have not been thoroughly analyzed in the literature. The aim of this study was to use the ambulatory phonation monitor (APM), a portable vocal dosimeter, to evaluate the variations in the vocal production of a group of patients suffering from moderate-to-severe HL treated with HA and the relationship between such modifications and quality of life (QoL). Materials and Methods: Twenty-six patients suffering from a variable degree of HL and treated with HA have been enrolled. Each of them underwent an evaluation before and 4 months after rehabilitation with HA. The analysis of daily voice production was carried out with the APM, while subjective QoL data were collected through the Speech, Spatial, and Qualities questionnaire (SSQ) and the International Outcome Inventory for Hearing Aids (IOI-HA). The differences in phonatory measurements and subjective evaluations before and after HA rehabilitation were assessed using Wilcoxon signed rank test. The Spearman correlation test was used to analyze the correlation between phonatory measurements, auditory measurements, and SSQ scores. Results: Significant differences in the APM parameters before and after HA rehabilitation were found. After 4 months of HA use, we recorded a significant increase in phonation time and percentage of phonation time and a significant decrease in average amplitude in dB SPL. We also found a significant increase in the SSQ scores after HA rehabilitation. Finally, we were able to detect low but significant correlations between phonatory measurements and SSQ results. Conclusions: The APM proved to be a useful instrument in the evaluation of the benefits of HA and its measurements can be used as indicators of the participation in communication and social life of patients with HL, which are strongly related to QoL.