Frequency thresholds of rat cochlear nerve fibers.

Activities of single cochlear nerve fibers of Wistar rats were recorded extracellularly. Best frequencies (BF) distributed from 0.50 to 62.6 kHz. The audiogram was made as the minimum boundary of the BF threshold distribution. The range of audible frequency was 0.54-63 kHz at 60 dB SPL and 0.15-67 kHz at 100 dB SPL. The lowest trough of the audiogram was 5 dB SPL at 41.2 kHz. There was the second trough of 10 dB SPL at 7.01 kHz leaving a notch between the two troughs. The shapes of the frequency-threshold curves (FTCs) of fibers were evaluated quantitatively and typical FTCs were shown as a function of BF.