Asynchronous neural activity recorded from the round window.

Voltage recorded from an electrode on the round window (RW) of guinea pig has characteristics that reflect the activity of auditory-nerve fibers in the absence of acoustic stimulation. Fast Fourier transformation (FFT) of the noise recorded from the RW electrode shows a broad spectral peak from 0.8-1.0 kHz. The magnitude of the biological noise is increased by high-frequency, bandlimited acoustic noise stimulation. Pure tones can suppress or enhance the spectral components around 0.8-1.0 kHz depending on frequency and intensity. Kainic acid applied to the intact RW membrane eliminates the biological noise (and the evoked cochlear whole-nerve responses) without alteration of the cochlear microphonic or the summating potential. The spectral characteristics of the biological noise seem to be related to the elemental waveform contributed by the individual auditory-nerve fibers to the voltage recorded at the RW electrode [Kiang et al., Electrocochleography, edited by R. J. Ruben, C. Elbering, and G. Solomon (University Park, Baltimore, 1976)].