Avian species differences in susceptibility to noise exposure

Hearing research, 1999

Previous studies of hair cell regeneration and hearing recovery in birds after acoustic overstimulation have involved relatively few species. Studies of the effects of acoustic overexposure typically report high variability. Though it is impossible to tell, the data so far also suggest there may be considerable species differences in the degree of damage and the time course and extent of recovery. To examine this issue, we exposed four species of birds (quail, budgerigars, canaries, and zebra finches) to identical conditions of acoustic overstimulation and systematically analyzed changes in hearing sensitivity, basilar papilla morphology, and hair cell number. Quail and budgerigars showed the greatest susceptibility to threshold shift and hair cell loss after overstimulation with either pure tone or bandpass noise, while identical types of overstimulation in canaries and zebra finches resulted in much less of a threshold shift and a smaller, more diffuse hair cell loss. All four species showed some recovery of threshold sensitivity and hair cell number over time. Canary and zebra finch hearing and hair cell number recovered to within normal limits while quail and budgerigars continued to have an approximately 20 dB threshold shift and incomplete recovery of hair cell number. In a final experiment, birds were exposed to identical wide-band noise overstimulation under conditions of artificial middle ear ventilation. Hair cell loss was substantially increased in both budgerigars and canaries suggesting that middle ear air pressure regulation and correlated changes in middle ear transfer function are one factor influencing susceptibility to acoustic overstimulation in small birds.

Proceedings of the National Academy of Sciences, 1974

Parakeets exposed for 72 hr to a 1/3-octave band of noise centered at 2.0 kHz have a maximum threshold shift at 2.0 kHz with little or no spread of threshold shift to lower or higher frequencies. These results differ from those observed in mammals and suggest significant differences between avian and mammalian peripheral auditory processing.

Naturwissenschaften, 1994

Journal of Comparative Psychology, 1987

Operant conditioning and a psychophysical tracking procedure were used to measure auditory thresholds for pure tones in quiet and in noise for seven species of small birds-the budgerigar, canary, cockatiel, European starling, song sparrow, swamp sparrow, and the zebra finch. Audibility curves are roughly similar among the seven birds, with the maximum sensitivity between 2 and 5 kHz and poorer sensitivity outside this narrow region. Critical ratios (signal-to-noise ratio at masked threshold) were calculated from pure-tone thresholds in noise. Except for the budgerigar, the critical ratio functions of all birds increase at the rate of 3 dB/octave. This pattern is typical of that observed in most vertebrates. Critical ratios in the budgerigar, on the other hand, decrease gradually from 0.5 kHz to 2.8 kHz and increase dramatically above 2.8 kHz. The present research demonstrates that the critical ratio function for the budgerigar is not only different from other vertebrates but also different from other birds.

Naturwissenschaften, 1984

rolled sheet and tested in the tensile mode at an elongation rate of 53.2x 10 6 m s -1 over the range 25 to 45 ~ Propolis exhibits an unusual behaviour on tensile deformation: there is a linear relationship between load and elongation from the origin of the curves to the maximum sustainable load. Thus, the yield stress coincides with the ultimate strength of the material. But, propolis like beeswax, is an entirely plastic material in the range 25 to 45 ~ so that this linearity is not an elastic one. On yield, propolis is highly ductile and flows about 200% before the necking thread finally fails. The tensile strength of propolis decreases 8-fold over the range of temperatures tested, and the yield strain some 3-fold over this range ). The stiffness remains virtually constant at lower temperatures with a major transition between 35 and 40 ~ The work to yield also decreases with increasing temperature as does the ductility of the substance.

The Journal of the Acoustical Society of America, 2011

Auditory brainstem responses (ABRs) were recorded in adult budgerigars, canaries, and zebra finches in quiet and in three levels of white noise for tone stimuli between 1 and 4 kHz. Similar to behavioral results, masked ABR thresholds increased linearly with increasing noise levels. When the three species are considered together, ABR-derived CRs were higher than behavioral CRs by 18-23 dB between 2 and 4 kHz and by about 30 dB at 1 kHz. This study clarifies the utility of using ABRs for estimating masked auditory thresholds in natural environmental noises in species that cannot be tested behaviorally. V

Journal of Comparative Physiology A, 1989

Hearing Research, 1999

Previous studies performed in anesthetized animals have shown differences between the acoustic responses of neurons recorded from the different divisions of the medial geniculate body (MGB). This study aimed at determining whether or not such differences are also expressed when neurons are recorded from awake animals. The auditory responses of 130 neurons of the auditory thalamus were determined in awake, restrained guinea pigs while the state of vigilance of the animals was continuously monitored. There were significantly more`on' phasic evoked responses and significantly fewer`non-responsive' or`labile' cells in the ventral division of the MGB (MGv) than in the other divisions. The response latencies and the variability of the latencies were smaller in the MGv than in the other divisions. The tuning of the neurons obtained from MGv and from the lateral part of the posterior complex were significantly sharper than those coming from the dorsal division of the MGB and the medial division. The mean threshold and the percentage of monotonic vs. non-monotonic intensity functions were not different in the subdivisions of the auditory thalamus. When compared with previous studies, the quantifications of the acoustic responses obtained in the present study gave values that differed from those reported under deep anesthesia, but were close to those reported under light anesthesia. Lastly, even if none of the physiological characteristic makes it possible, by itself, to determine the locus of recordings in the auditory thalamus, we conclude that the physiological characteristics of the evoked responses obtained in MGv differ from those of other divisions. ß 1999 Elsevier Science B.V. All rights reserved. 0378-5955 / 99 / $^see front matter ß 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 -5 9 5 5 ( 9 9 ) 0 0 0 2 6 -X

Journal of Comparative Physiology A: Sensory, Neural, and Behavioral Physiology, 2002

The physical mechanisms of sound generation in the vocal organ, the syrinx, of songbirds have been investigated mostly with indirect methods. Recent direct endoscopic observation identified vibrations of the labia as the principal sound source. This model suggests sound generation in a pulse-tone mechanism similar to human phonation with the labia forming a pneumatic valve. The classical avian model proposed that vibrations of the thin medial tympaniform membranes are the primary sound generating mechanism. As a direct test of these two hypotheses we ablated the medial tympaniform membranes in two species (cardinal and zebra finch) and found that both were still able to phonate and sing without functional membranes. Small changes in song structure (harmonic emphasis, frequency control) occurred after medial tympaniform membrane ablation and suggest that the medial tympaniform membranes play a role in adjusting tension on the labia. Such a role is consistent with the fact that the medial tympaniform membranes are directly attached to the medial labia. There is no experimental support for a third hypothesis, proposing an aerodynamic model for generation of tonal sounds. Indirect tests (song in heliox atmosphere) as well as direct (labial vibration during tonal sound) measurements of syringeal vibrations support a vibration-based soundgenerating mechanism even for tonal sounds.

Hearing Research, 2010

Belgian Waterslager (BW) canaries have an inherited hearing loss due to missing and abnormal hair cells, but it is unclear whether the loss is congenital or developmental. We used auditory brainstem responses and scanning electron microscopy to describe the development of auditory sensitivity and hair cell abnormalities in BW and non-BW canary. In both strains, adult ABR thresholds were higher than behavioral thresholds, but BW canaries exhibited higher thresholds than non-BW canaries across all frequencies. Immediately post-hatch, ABR thresholds and hair cell numbers were similar in both strains. Two weeks later, thresholds were significantly higher in BW canaries and hair cell number progressively decreased as the birds aged. These data show that in BW canaries: the peripheral auditory system is functionally similar to non-BW canary from hatch to 2 weeks, ABR thresholds improve during this developmental period, actually becoming better than those of adults, but then worsen as the bird continues to age, and hair cell number and appearance is similar to non-BW canaries at hatch but progressively declines after 30 days of age. These data show that the hearing loss characteristic of BW canaries is, at least in part, developmental and is established by the time song learning begins.