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Electrophysiological study of the maturation of auditory responses from the inner ear of the chick
Insights
Auditory function in chicks matures from day 15 of incubation to post-hatching day 1. Cochlear development shows low-frequency responses maturing before high-frequency ones, impacting auditory ontogeny.
Area of Science:
- Auditory Neuroscience
- Developmental Biology
- Electrophysiology
Background:
- The chick basilar papilla is a model for studying auditory development.
- Understanding the maturation of electrophysiological functions is crucial for auditory ontogeny.
Purpose of the Study:
- To investigate the developmental trajectory of three electrophysiological functions in the chick basilar papilla.
- To characterize the maturation of auditory thresholds, input-output functions, and tuning properties.
Main Methods:
- Recording compound action potentials (AP) at the round window in chick embryos (E15-P1).
- Utilizing tone-on-tone masking to assess auditory tuning properties (Q10).
- Examining auditory thresholds and intensity-amplitude functions across developmental stages.
Main Results:
- Auditory thresholds continuously matured from E15 to P1, with low frequencies maturing before high frequencies.
- Input-output functions showed regular maturation without the two-slope pattern observed in mammals.
- Tuning properties (Q10) matured earlier than thresholds, reaching adult values by E17 (500 Hz) and E19 (1000 Hz).
Conclusions:
- The chick basilar papilla exhibits a low-to-high frequency maturation trend in auditory responses.
- Early maturation of tuning properties suggests cochlear transduction changes are key to auditory development.
- Findings offer insights into the developmental plasticity of the auditory system.
Abstract:
Three electrophysiological functions of the chick basilar papilla were studied during development by recording the compound actin potential (AP) at the round window. The auditory thresholds showed a continuous maturation between the fifteenth day of incubation (E15) and the first post-hatching day (P1), when they attained adult values. Responses matured first to low frequencies and later to high frequency stimuli. The input-output (intensity-amplitude) functions matured regularly and never demonstrated the classical two slopes seen in mammals. The tuning properties, studied by tone-on-tone masking of the AP, achieved mature values before the thresholds; the Q10s reached adult values at E17 for a 500-Hz probe tone and at E19 for a 1000-Hz probe tone. The fact that a low-to-high frequency development trend was found with the embryonic middle ear cleared of fluids further suggests that this property of auditory ontogeny may be a function of changes in the transduction properties of the cochlea.