Frequency Modulation During Song in a Suboscine Does Not Require Vocal Muscles
01 May 2008-Journal of Neurophysiology (American Physiological Society)-Vol. 99, Iss: 5, pp 2383-2389
TL;DR: This work investigates sound production and control of sound frequency in the Great Kiskadee by recording air sac pressure and vocalizations during spontaneously generated song and assumes a nonlinear restitution force for the oscillating membrane folds in a two mass model of sound production to reproduce the frequency modulations of the observed vocalizations.
Abstract: The physiology of sound production in suboscines is poorly investigated. Suboscines are thought to develop song innately unlike the closely related oscines. Comparing phonatory mechanisms might therefore provide interesting insight into the evolution of vocal learning. Here we investigate sound production and control of sound frequency in the Great Kiskadee (Pitangus sulfuratus) by recording air sac pressure and vocalizations during spontaneously generated song. In all the songs and calls recorded, the modulations of the fundamental frequency are highly correlated to air sac pressure. To test whether this relationship reflects frequency control by changing respiratory activity or indicates synchronized vocal control, we denervated the syringeal muscles by bilateral resection of the tracheosyringeal nerve. After denervation, the strong correlation between fundamental frequency and air sac pressure patterns remained unchanged. A single linear regression relates sound frequency to air sac pressure in the intact and denervated birds. This surprising lack of control by syringeal muscles of frequency in Kiskadees, in strong contrast to songbirds, poses the question of how air sac pressure regulates sound frequency. To explore this question theoretically, we assume a nonlinear restitution force for the oscillating membrane folds in a two mass model of sound production. This nonlinear restitution force is essential to reproduce the frequency modulations of the observed vocalizations.
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TL;DR: A growing number of studies ask whether and how bird songs vary between areas with low versus high levels of anthropogenic noise as discussed by the authors and find that birds are seen to sing at higher frequencies in urban versus rural populations, presumably because of selection for higher-pitched songs in the face of low-frequency urban noise.
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Cites background from "Frequency Modulation During Song in..."
...A strong correlation between subsyringeal pressure and vocalization frequencywas also found in a suboscine bird, the great kiskadee, Pitangus sulphuratus (Amador et al. 2008), providing further evidence that driving pressure and frequency are biomechanically linked....
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TL;DR: The results show that the syringeal skeleton is optimized for low weight driven by physiological constraints on song production, and a cartilaginous structure suited to play a crucial role in the uncoupling of sound frequency and amplitude control, which permits a novel explanation of the evolutionary success of songbirds.
Abstract: Like human infants, songbirds learn their species-specific vocalizations through imitation learning. The birdsong system has emerged as a widely used experimental animal model for understanding the underlying neural mechanisms responsible for vocal production learning. However, how neural impulses are translated into the precise motor behavior of the complex vocal organ (syrinx) to create song is poorly understood. First and foremost, we lack a detailed understanding of syringeal morphology. To fill this gap we combined non-invasive (high-field magnetic resonance imaging and micro-computed tomography) and invasive techniques (histology and micro-dissection) to construct the annotated high-resolution three-dimensional dataset, or morphome, of the zebra finch (Taeniopygia guttata) syrinx. We identified and annotated syringeal cartilage, bone and musculature in situ in unprecedented detail. We provide interactive three-dimensional models that greatly improve the communication of complex morphological data and our understanding of syringeal function in general. Our results show that the syringeal skeleton is optimized for low weight driven by physiological constraints on song production. The present refinement of muscle organization and identity elucidates how apposed muscles actuate different syringeal elements. Our dataset allows for more precise predictions about muscle co-activation and synergies and has important implications for muscle activity and stimulation experiments. We also demonstrate how the syrinx can be stabilized during song to reduce mechanical noise and, as such, enhance repetitive execution of stereotypic motor patterns. In addition, we identify a cartilaginous structure suited to play a crucial role in the uncoupling of sound frequency and amplitude control, which permits a novel explanation of the evolutionary success of songbirds.
187 citations
TL;DR: The HVC precisely encodes vocal motor output through activity at the times of extreme points of movement trajectories, and it is proposed that the sequential activity of HVC neurons is used as a 'forward' model, representing the sequence of gestures in song to make predictions on expected behaviour and evaluate feedback.
Abstract: Quantitative biomechanical models can identify control parameters that are used during movements, and movement parameters that are encoded by premotor neurons. We fit a mathematical dynamical systems model including subsyringeal pressure, syringeal biomechanics and upper-vocal-tract filtering to the songs of zebra finches. This reduces the dimensionality of singing dynamics, described as trajectories (motor 'gestures') in a space of syringeal pressure and tension. Here we assess model performance by characterizing the auditory response 'replay' of song premotor HVC neurons to the presentation of song variants in sleeping birds, and by examining HVC activity in singing birds. HVC projection neurons were excited and interneurons were suppressed within a few milliseconds of the extreme time points of the gesture trajectories. Thus, the HVC precisely encodes vocal motor output through activity at the times of extreme points of movement trajectories. We propose that the sequential activity of HVC neurons is used as a 'forward' model, representing the sequence of gestures in song to make predictions on expected behaviour and evaluate feedback.
160 citations
TL;DR: Comparison of patterns of song adjustment to noise in oscines and suboscines in Brazil and Mexico City suggests that song learning and/or song plasticity allows adaptation to new habitats and that this selective advantage may be linked to the evolution ofsong learning and plasticity.
Abstract: Song learning has evolved within several avian groups. Although its evolutionary advantage is not clear, it has been proposed that song learning may be advantageous in allowing birds to adapt their songs to the local acoustic environment. To test this hypothesis, we analysed patterns of song adjustment to noisy environments and explored their possible link to song learning. Bird vocalizations can be masked by low-frequency noise, and birds respond to this by singing higher-pitched songs. Most reports of this strategy involve oscines, a group of birds with learning-based song variability, and it is doubtful whether species that lack song learning (e.g. suboscines) can adjust their songs to noisy environments. We address this question by comparing the degree of song adjustment to noise in a large sample of oscines (17 populations, 14 species) and suboscines (11 populations, 7 species), recorded in Brazil (Manaus, Brasilia and Curitiba) and Mexico City. We found a significantly stronger association between minimum song frequency and noise levels (effect size) in oscines than in suboscines, suggesting a tighter match in oscines between song transmission capacity and ambient acoustics. Suboscines may be more vulnerable to acoustic pollution than oscines and thus less capable of colonizing cities or acoustically novel habitats. Additionally, we found that species whose song frequency was more divergent between populations showed tighter noise-song frequency associations. Our results suggest that song learning and/or song plasticity allows adaptation to new habitats and that this selective advantage may be linked to the evolution of song learning and plasticity.
73 citations
TL;DR: It is suggested that adjustments in song frequency and amplitude are largely independent and, thus, can be complementary rather than alternative vocal adjustments to noise.
70 citations
References
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TL;DR: In this article, the authors analyzed two symmetric two-mass models of the avian syrinx, and showed that the occurrence of collisions and the intensity of harmonics depend strongly on the configuration of the Syrinx.
Abstract: We analyze two symmetric two-mass models of the avian syrinx. Our first model applies to songbirds and is a rescaled version of the well-known human two-mass model. Our second model (trapezoidal model) introduces a smoother geometry and is used to simulate the ring dove (Streptopelia risoria) syrinx. Simulations show that both models exhibit self-sustained vibrations. We show that the occurrence of collisions and the intensity of harmonics depend strongly on the configuration of the syrinx. The songbird model does not present instabilities. The trapezoidal model, however, displays coexisting limit-cycles that represent vibrations with, and without collisions at the same pressure. Register-like transitions are accompanied by subharmonics and deterministic chaos.
16 citations
7 citations
TL;DR: Factors affecting the tension on the external tympaniform membranes of the syrinx during respiration and vocalization were studied in 35 adult chickens.
Abstract: Factors affecting the tension on the external tympaniform membranes of the syrinx during respiration and vocalization were studied in 35 adult chickens. These membranes are controlled by the interacti
6 citations
6 citations