Bohne, B.A. and Dooling, R.J. (1974). Morphological changes in the ears of noise-exposed parakeets. J. Acoust. Soc. Am. 55, S77.
Parakeets exposed to
-octave
bands of noise for 12 or more hours sustain asymptotic threshold
shifts (Dooling and Saunders). The ears of three parakeets from the
Dooling and Saunders study were prepared for phase-contrast
microscopic examination as embedded whole mounts after final
audiograms had been obtained. Findings in these ears were then
compared to ears of other parakeets exposed for 12 hours to a
-octave
band of noise centered at 2 kHz with a sound pressure level of 76,
86, or 106 dB. The ears of half the parakeets were prepared
for microscopic examination 30 minutes following exposure, while the rest
were prepared after the birds had recovered from their ATS.
Preliminary findings in parakeet ears with ATS include: no sensory
cell loss, no tectorial membrane displacement, no reticular lamina breakage,
and no abnormalities in the stereocilia. In addition, the cytoplasm
of some tall hair cells bulged from the surface of the basilar
papilla, thus separating nerve endings from the hair cell bases. This
latter feature was not present in parakeet ears which had recovered
from ATS.