Glottal opening and closing events investigated by electroglottography and super-high-speed video recordings

International audiencePrevious research has suggested that the peaks in the first derivative (dEGG) of the electroglottographic (EGG) signal are good approximate indicators of the events of glottal opening and closing. These findings were based on high-speed video (HSV) recordings with frame rates 10 times lower than the sampling frequencies of the corresponding EGG data. The present study attempts to corroborate these previous findings, utilizing super-HSV recordings. The HSV and EGG recordings (sampled at 27 and 44 kHz, respectively) of an excised canine larynx phonation were synchronized by an external TTL signal to within 0.037 ms. Data were analyzed by means of glottovibrograms, digital kymograms, the glottal area waveform and the vocal fold contact length (VFCL), a new parameter representing the time-varying degree of 'zippering' closure along the anterior-posterior (A-P) glottal axis. The temporal offsets between glottal events (depicted in the HSV recordings) and dEGG peaks in the opening and closing phase of glottal vibration ranged from 0.02 to 0.61 ms, amounting to 0.24-10.88% of the respective glottal cycle durations. All dEGG double peaks coincided with vibratory A-P phase differences. In two out of the three analyzed video sequences, peaks in the first derivative of the VFCL coincided with dEGG peaks, again co-occurring with A-P phase differences. The findings suggest that dEGG peaks do not always coincide with the events of glottal closure and initial opening. Vocal fold contacting and de-contacting do not occur at infinitesimally small instants of time, but extend over a certain interval, particularly under the influence of A-P phase differences

The graviportal spine : epaxial muscles of the African savanna elephant (Loxodonta africana)

DATA AVAILABILITY: The data that support the findings of this study are available from the corresponding author C. M. V. B. upon reasonable request.In this study, we present not only a new and detailed anatomical description of the epaxial muscles and adjacent ligamentous and fascial structures in the African sa-vanna elephant but also a structural and functional comparison with other Afrotherian mammals and some domestic quadrupeds. All structures were examined by means of standard anatomical techniques. The back of the largest land mammal is a crucial part of trunk construction according to the bow and string concept, which is applied also in other quadrupedal animals. The epaxial muscles of the African savanna elephant play an important role in the biomechanical properties of the entire back and in support-ing and moving the heavy head. Situated in the short cervical region of the African savanna elephant is a large mass comprised of numerous muscle individuals together with a well-developed ligamentum nuchae. Parts of the mm. interansversarii ventralis cervicis form a strong muscle belly, which was named the m. intertransversarius lon-gus. Whereas the head is held in a high or extended position most of the time during locomotion, the head and neck are highly mobile while the animal is foraging or so-cially interacting. Movements between the elements of the thoracic and lumbar spine are likely to be very limited due to the obvious rigidity of the bony vertebral column. Aponeuroses surrounding long epaxial muscles could contribute to an energy-saving mechanism, which is active during both stance and locomotion. The well-developed m. serratus dorsalis cranialis helps in facilitating effective breathing in an animal, which is equipped with an unusual pleural structure.International Relations Office of the University of Veterinary Medicine, Vienna, Austria.http://wileyonlinelibrary.com/journal/aheAnatomy and Physiolog

Domestic cat larynges can produce purring frequencies without neural input

Most mammals produce vocal sounds according to the myoelastic-aerodynamic (MEAD) principle, through self-sustaining oscillation of laryngeal tissues.1,2 In contrast, cats have long been believed to produce their low-frequency purr vocalizations through a radically different mechanism involving active muscle contractions (AMC), where neurally driven electromyographic burst patterns (typically at 20–30 Hz) cause the intrinsic laryngeal muscles to actively modulate the respiratory airflow. Direct empirical evidence for this AMC mechanism is sparse.3 Here, the fundamental frequency (fo) ranges of eight domestic cats (Felis silvestris catus) were investigated in an excised larynx setup, to test the prediction of the AMC hypothesis that vibration should be impossible without neuromuscular activity, and thus unattainable in excised larynx setups, which are based on MEAD principles. Surprisingly, all eight excised larynges produced self-sustained oscillations at typical cat purring rates. Histological analysis of cat larynges revealed the presence of connective tissue masses, up to 4 mm in diameter, embedded in the vocal fold.4 This vocal fold specialization appears to allow the unusually low fo values observed in purring. While our data do not fully reject the AMC hypothesis for purring, they show that cat larynges can easily produce sounds in the purr regime with fundamental frequencies of 25 to 30 Hz without neural input or muscular contraction. This strongly suggests that the physical and physiological basis of cat purring involves the same MEAD-based mechanisms as other cat vocalizations (e.g., meows) and most other vertebrate vocalizations but is potentially augmented by AMC

Microscopic morphology of the elephant's hoof

As a result of the lack of basic microscopic anatomy of the elephants' foot, this study deals with the normal microscopic morphology of both the Asian (Elephas maximus) and African (Loxodonta africana) elephant foot with consideration of pathologic changes. A total of 727 histologic samples from defined locations of 24 hooves of both species (17 Asian and seven African species) were studied, measured, and evaluated. Minor differences between the feet and species are seen histologically. Poor horn quality in captive elephants' hooves and loci of minor resistance in captive and wild animals are detected. The thickness of the weight-bearing surface of the captive elephants' hooves is histologically measured as "very thin" (about 10 mm). The normal histologic findings provide a basis for assessing histopathologic changes and especially horn quality. The histologic findings might explain some of the foot problems, but they also give rise to questions about the quality and correctness of current husbandry technique