FRACTAL NOISE STRENGTH IN AUDITORY-NERVE FIBER RECORDINGS

Discharge patterns recorded from single auditory-nerve fibers have dem onstrated long-range dependence, with the count variance-to-mean ratio growing as a power of the counting time for times greater than 0.1-1 s. The intent of this study is-to provide a large dataset to enable a more detailed investigation of this phenomenon. Based on 108 recording s from a cat, we conclude that the presence of the fractal noise in th e discharge rate is : Independent of characteristic frequency and stim ulus level, but does depend on discharge rate. We measured the low-fre quency power of the fractal noise, finding its coefficient of variatio n to range between 6% and 26% and to decrease as firing rate increases . Such behavior is consistent with multiplicative fractal variations i n models of the hair cell membrane permeability to neurotransmitter. M easured standard deviations of spike rate correspond to a sound-pressu re level difference limen of approximately 1 dB. (C) 1996 Acoustical S ociety of America.