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Cochlear nerve activity after intense sound exposure in neonatal chicks
J C Saunders1, D E Doan, C P Poje
1Department of Otorhinolaryngology-Head and Neck Surgery, University of Pennsylvania, Philadelphia, USA.
Journal of Neurophysiology
|August 1, 1996
Summary
Neonatal chicks exposed to loud noise showed temporary hearing loss and altered neural responses. Full recovery of neural function occurred after 12 days, but some abnormalities persisted, linked to structural damage.
Area of Science:
- Auditory Neuroscience
- Ototoxicity Research
- Neurobiology of Hearing
Background:
- Neonatal auditory system is vulnerable to noise-induced damage.
- Understanding recovery mechanisms is crucial for hearing loss treatment.
Purpose of the Study:
- To investigate cochlear nerve single-neuron responses in neonatal chicks after noise exposure.
- To assess the effects of noise exposure and recovery on neural tuning and activity.
- To correlate neural recovery with structural changes in the auditory system.
Main Methods:
- Exposure of neonatal chicks to a 120-dB SPL pure tone (0.9 kHz) for 48 hours.
- Electrophysiological recordings of cochlear nerve single-neuron activity (903 cells).
- Analysis of characteristic frequency (CF), CF threshold, tuning sharpness (Q10 dB), spontaneous activity, and rate-intensity functions.
Main Results:
- Noise exposure caused frequency-dependent threshold shifts and suppressed spontaneous activity.
- Tuning (Q10 dB) deteriorated at higher frequencies (>0.5 kHz).
- After 12 days recovery, CF threshold, Q10 dB, and spontaneous activity normalized, but abnormal rate-intensity functions persisted in specific frequency regions.
Conclusions:
- The neonatal chick cochlear nerve exhibits significant noise-induced changes.
- Functional recovery is substantial within 12 days, with neural tuning and thresholds normalizing.
- Persistent abnormalities in rate-intensity functions suggest lasting structural damage, particularly in the tectorial membrane and short hair cell region.