Cervids with different vocal behavior demonstrate different viscoelastic properties of their vocal folds

Abstract

The authors test the hypothesis that vocal fold morphology and biomechanical properties covary with species-specific vocal function. They investigate mule deer (Odocoileus hemionus) vocal folds, building on, and extending data on a related cervid, the Rocky Mountain elk (Cervus elaphus nelsoni). The mule deer, in contrast to the elk, is a species with relatively little vocal activity in adult animals. Mule deer and elk vocal folds show the typical three components of the mammalian vocal fold (epithelium, lamina propria and thyroarytenoid muscle). The vocal fold epithelium and the lamina propria were investigated in two sets of tensile tests. First, creep rupture tests demonstrated that ultimate stress in mule deer lamina propria is of the same magnitude as in elk. Second, cyclic loading tests revealed similar elastic moduli for the vocal fold epithelium in mule deer and elk. The elastic modulus of the lamina propria is also similar between the two species in the low-strain region, but differs at strains larger than 0.3. Sex differences in the stress–strain response, which have been reported for elk and human vocal folds, were not found for mule deer vocal folds. The laminae propriae in mule deer and elk vocal folds are comparatively large. In general, a thick and uniformly stiff lamina propria does not self-oscillate well, even when high subglottic pressure is applied. If the less stiff vocal fold seen in elk is associated with a differentiated lamina propria it would allow the vocal fold to vibrate at high tension and high subglottic pressure. The results of this study support the hypothesis that viscoelastic properties of vocal folds varies with function and vocal behavior.

Elasticity and stress relaxation of rhesus monkey (Macaca mulatta) vocal folds

“…Hirano 1974;Hahn et al, 2006a;Hahn et al, 2006b) and many other mammal vocal folds (e.g. Kurita et al, 1983;Riede et al, 2010), fat cells (Fig.5E). All four components are not equally distributed and are likely contributing to differentiated viscoelastic properties throughout the lamina propria, giving rise to functionally different layers in the lamina propria.…”

“…We corrected all mass measurements by 10%, accounting for mass gain, following earlier studies (Riede and Titze, 2008;Riede et al, 2010) as well as a measurement in one rhesus monkey vocal fold. We adapted density values from an earlier study (Min et al, 1995).…”

“…At strains larger than 20-30%, the stress response is highly nonlinear and demonstrates quantitative differences between individuals, sexes, as well as species (Haji, 1990;Min et al, 1995;Chan et al, 2007;Zhang et al, 2009;Riede et al, 2010). When vocal folds are strained, some stress is released ) and would cause a drop in f 0 if not compensated, for example, by further stretching.…”

Morphological basis for the evolution of acoustic diversity in oscine songbirds

“…However, neural control can only adjust F0 within the physical limits, which are determined by the morphology and composition of the vibrating tissue. Previous work in songbirds [14] and mammals [15] showed that mechanical differences of labia are associated with vocal differences between species. In vivo experiments demonstrated the role of labia in F0 determination and the role of muscles in labia adjustment [16 -19], and computational modelling illustrated how muscle control and labial dynamics contribute to generate diverse features of sound [20].…”

The Microfibril-Elastin Fiber System Distribution in Left Atrioventricular Valve of the Rat

“…Elastic fibers play a role in connective tissues that are normally subject to stretch and expansible forces, because they provide the mechanical basis of numerous body functions, such as respiration (Ramirez & Sakai, 2010), phonation (Riede et al, 2010), and maintenance of vascular tone (Ramirez & Sakai). Elastic fibers are made of fibrillin microfibrils, which surround and are embedded in an amorphous core of elastin (Ramirez & Dietz, 2009).…”