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Updated: Jul 28, 2026
In Ovo Electroporation in the Chicken Auditory Brainstem
Published on: June 9, 2017
The growth of hearing loss in neonatal chicks exposed to intense pure tones
J C Saunders1, A J Torsiglieri, R M DeDio
1Department of Otorhinolaryngology and Human Communication, University of Pennsylvania, Philadelphia.
Insights
Intense noise exposure significantly harms hearing sensitivity and frequency selectivity in young chicks, with effects worsening over time. Cochlear damage correlates with these auditory system impairments.
Area of Science:
- Auditory Neuroscience
- Ototoxicity Research
- Animal Models in Hearing Science
Background:
- Noise-induced hearing loss is a significant health concern.
- Understanding the mechanisms of auditory damage is crucial for prevention and treatment.
- Chick models offer a valuable system for studying auditory development and noise effects.
Purpose of the Study:
- To investigate the effects of prolonged intense noise exposure on auditory sensitivity and frequency selectivity in one-day-old chicks.
- To determine the relationship between exposure duration and the extent of hearing impairment.
- To explore potential early and late effects of noise exposure on auditory processing.
Main Methods:
- One-day-old chicks were exposed to a 0.9 kHz pure tone at 120 dB SPL for durations ranging from 1 to 200 hours.
- Auditory brainstem responses were recorded to measure absolute hearing thresholds and frequency selectivity.
- Thresholds were assessed at 10 frequencies (0.1–4.5 kHz), and frequency selectivity was evaluated using simultaneous masking tuning curves.
Main Results:
- A maximum threshold shift of approximately 57 dB was observed at 1.3 kHz after 48–200 hours of exposure.
- Noise exposure led to a significant decrease in frequency selectivity (tuning sharpness) above 0.9 kHz, with a maximum reduction of 54% by 48 hours.
- Low-frequency tuning (below 0.9 kHz) showed no systematic loss in selectivity, and both sensitivity and selectivity changes correlated with cochlear injury patterns.
Conclusions:
- Prolonged exposure to intense noise causes significant and lasting hearing loss and reduced frequency selectivity in developing auditory systems.
- The findings suggest distinct early and late phases of noise-induced auditory damage.
- The study highlights the vulnerability of the developing cochlea to acoustic trauma and provides insights into the underlying mechanisms of hearing impairment.
Abstract:
One-day-old chicks were exposed to an intense pure tone (0.9 kHz, 120 dB SPL) and assigned to one of eight groups based on continuous exposure durations from 1 to 200 h. As each animal was removed from the exposure, it was anesthetized and an electrode was placed in the nucleus magnocellularis. Sound-evoked potentials were used to measure absolute thresholds and frequency selectivity. Thresholds were measured at 10 frequencies between 0.1 and 4.5 kHz while frequency selectivity was assessed by a simultaneous masking tuning-curve procedure at five probe-tone frequencies between 0.3 and 2.5 kHz. Threshold shift was greatest at 1.3 kHz and reached a maximum loss of approximately 57 dB between 48 and 200 h of exposure. The shape of the threshold-shift curve as a function of exposure duration (for frequencies between 0.9 and 2.5 KHz) suggested the presence of an early and late effect. The loss in tuning sharpness was evaluated by comparing the values of Q10 dB for control and exposed tuning curves and expressing the difference between them as a percent change. Probe-tone tuning curves above 0.9 kHz became less selective as exposure duration increased. A maximum decrease in tuning of about 54 percent was reached by 48 h and this remained constant to 200 h. The low-frequency tuning curves (below 0.9 kHz) did not show any systematic loss in selectivity. The changes in sensitivity and selectivity are discussed in relation to the patterns of cochlear injury that occurred on the basilar papilla as exposure duration lengthened.
