Eighth nerve fiber firing features in normal-hearing rabbits.
Neural activity of single eighth nerve fibers was recorded with glass microelectrodes in anesthetized normal-hearing rabbits. The units had a spontaneous rate ranging from 0 to approximately 120 spikes/s. In a large number of fibers this rate was below 2 spikes/s. The frequency tuning curves (FTCs) had a tip and a tail region for fibers with a high or medium characteristic frequency (CF). For low-frequency units the FTC was more symmetrically U-shaped. The tip threshold reached the behavioral threshold and units with thresholds of up to more than 60 dB above the mean behavioral threshold were found. There was a weak negative correlation between spontaneous rate and tip threshold. Frequency selectivity, Q10, was about 2 for units with CF below 2 kHz and about 5 for those with CF above 4 kHz. The peristimulus time (PST) histogram showed an initial peak, a plateau, and poststimulus inhibition. For the majority of fibers the dynamic range was 20-30 dB. Some fibers did not reach saturation within the stimulus intensity available. The tip-to-tail distance was 50 dB for high-frequency units at one octave below CF, a matter of potential interest for further studies of animals with inner ear lesions.
Borg
E
E
Department of Audiology, Karolinska Hospital, Stockholm, Sweden.
Engström
B
B
Linde
G
G
Marklund
K
K
D000818:Animals; D001309:Auditory Threshold / Q000502:physiology; D005072:Evoked Potentials, Auditory; D006198:Hair Cells, Auditory / Q000502:physiology; D006309:Hearing / Q000502:physiology*; D009412:Nerve Fibers / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D010897:Pitch Discrimination / Q000502:physiology; D011817:Rabbits; D012016:Reference Values; D000159:Vestibulocochlear Nerve / Q000502:physiology*