Related Experiment Videos
Repeated TTS exposures in monkeys: alterations in hearing, cochlear structure, and single-unit thresholds
The Journal of the Acoustical Society of America
|May 1, 1987
Summary
Repeated noise exposure can cause permanent hearing loss, initially affecting neural responses before causing measurable damage. This study shows that prolonged sound exposure in monkeys led to high-frequency hearing loss and cochlear damage.
Area of Science:
- Auditory Neuroscience
- Ototoxicology
- Hearing Science
Background:
- Noise-induced hearing loss (NIHL) assessment depends on measurement sensitivity.
- Single auditory neuron responses may indicate early physiological damage from noise.
- Temporary threshold shift (TTS) episodes might cumulatively cause permanent threshold shift (PTS).
Purpose of the Study:
- To investigate if repeated temporary threshold shifts (TTS) lead to permanent threshold shifts (PTS) in monkeys.
- To determine if single-unit neural activity changes precede behavioral or histological evidence of hearing damage.
- To correlate behavioral, neural, and histological findings after chronic noise exposure.
Main Methods:
- Monkeys were exposed to TTS-inducing sounds for 6 or 18 months.
- Behavioral hearing thresholds were measured using a reaction-time task.
- Auditory nerve and cochlear nucleus neural activity was recorded, followed by histological examination of cochleas.
Main Results:
- Monkeys exposed for 18 months showed significant high-frequency hearing loss and cochlear damage.
- Neural thresholds in the cochlear nucleus correlated with behavioral threshold shifts.
- Even without behavioral loss, 6 months of exposure caused elevated neural thresholds and cochlear lesions.
Conclusions:
- Chronic TTS exposure can lead to permanent high-frequency hearing loss in primates.
- Changes in single-unit neural thresholds may serve as an early indicator of noise-induced cochlear damage.
- Histological damage to the organ of Corti and nerve fibers corresponds to functional hearing deficits.