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Activity patterns of primary auditory-nerve fibres in chickens: development of fundamental properties
1Institut für Zoologie, Technischen Universität München, Garching, F.R.G.
Insights
Chicken auditory nerve fibers show mature tuning by post-hatching day 2, but their intensity functions develop later. This study reveals key insights into auditory system development in young chickens.
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Developmental Neuroscience
Background:
- The development of the auditory system is crucial for sensory processing.
- Understanding changes in auditory nerve fiber activity during post-hatching development provides insights into neural maturation.
Purpose of the Study:
- To investigate the activity patterns of single auditory-nerve fibers in chickens.
- To determine if these patterns change during post-hatching development (P2 vs. P21).
Main Methods:
- Electrophysiological recordings from cochlear ganglion fibers in chickens at two age groups (post-hatching day 2 and 21).
- Analysis of spontaneous and sound-evoked activity patterns, including tuning characteristics and rate-intensity functions, under anesthesia.
Main Results:
- Spontaneous activity rates were similar between age groups (20.5-23 spikes/s).
- Tuning characteristics (frequency range, suppression, Q10dB) were statistically indistinguishable between P2 and P21 chickens.
- Differences observed in high-frequency thresholds and rate-intensity functions between the two age groups.
Conclusions:
- Chicken primary auditory fiber tuning properties are mature by post-hatching day 2.
- Auditory nerve fiber intensity functions continue to develop beyond post-hatching day 2.
Abstract:
We have examined the activity patterns of single auditory-nerve fibers in the chicken and tested for possible changes during post-hatching development. For this purpose, we recorded from fibres in the cochlear ganglion of chickens of two age groups (about P2 and P21) and investigated their spontaneous and sound-evoked activity patterns under nembutal-chloralhydrate anaesthesia. The spontaneous activity of primary auditory neurones was irregular, the average rates were between 20.5 (P2) and 23 (P21) spikes/s. Many low-frequency fibres from both age groups showed preferred intervals in their spontaneous activity. Tuning characteristics, including the range of characteristic frequencies, the presence of primary and two-tone suppression, the slopes of tuning-curve flanks and Q10dB values were similar to those previously reported for the starling and were statistically indistinguishable between the two age groups. However, there was a difference in fibre thresholds at the highest frequencies. Systematic differences were also present between the two age groups with regard to some characteristics of the rate-intensity functions. These data indicate that whereas the tuning properties of primary auditory fibres of the chicken cochlea are mature as early as post-hatching day 2, the intensity functions are not.