Activity patterns of primary auditory-nerve fibres in chickens: development of fundamental properties.
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.
Manley
G A
GA
Institut für Zoologie, Technischen Universität München, Garching, F.R.G.
Kaiser
A
A
Brix
J
J
Gleich
O
O
D000161:Acoustic Stimulation; D000200:Action Potentials; D000818:Animals; D000831:Animals, Newborn; D002645:Chickens; D005072:Evoked Potentials, Auditory; D008297:Male; D009412:Nerve Fibers / Q000502:physiology; D013136:Spiral Ganglion / Q000502:physiology; D000159:Vestibulocochlear Nerve / Q000254:growth & development / Q000502:physiology*