EFFECT OF HIGH-FREQUENCY INTERRUPTED NOISE EXPOSURES ON EVOKED-POTENTIAL THRESHOLDS, DISTORTION-PRODUCT OTOACOUSTIC EMISSIONS, AND OUTER HAIR CELL LOSS
M. Subramaniam et al., EFFECT OF HIGH-FREQUENCY INTERRUPTED NOISE EXPOSURES ON EVOKED-POTENTIAL THRESHOLDS, DISTORTION-PRODUCT OTOACOUSTIC EMISSIONS, AND OUTER HAIR CELL LOSS, Ear and hearing, 16(4), 1995, pp. 372-381
The effect of high-frequency interrupted noise exposures on evoked pot
ential (EP) thresholds, distortion-product otoacoustic emissions (DPOA
Es), and status of the outer hair cells was studied with the aim of un
derstanding the correspondence among the three measures. Animal subjec
ts were exposed to an octave band noise centered at 4 kHz at 85 dB SPL
for 6 hr/day for 10 days. EP and DPOAE recordings were made before th
e exposure and on days 1, 2, 4, 6, 8, and 10 of exposure. A final set
of measurements were made 5 days after the last exposure, following wh
ich the animals were sacrificed and their cochleas were examined using
scanning electron microscopy. Both EPs and DPOAEs showed a worsening
of auditory function after the first exposure and then showed a progre
ssive recovery toward baseline. However, there was no consistent relat
ionship between changes in EP thresholds and changes in DPOAEs nor wer
e there any systematic changes in outer Flair cells that corresponded
with the changes in DPOAEs. Furthermore, EP thresholds often revealed
considerable deficits in function while DPOAEs were normal.