Effect of click spectrum and polarity on round window N1N2 response in the rat

The effect of the duration of click stimuli on the compound action potential recorded from the round window in the rat and the effect of low-pass filtering of short click sounds were studied. Thus the intensity functions of the round window N1 potential have a two-segment course and there is a difference in the response to rarefaction and condensation clicks, depending upon the content of low-frequency components in the click stimulus. The intensity function of the rat's response to broadband clicks does not show the same two-segment course as has been reported in experiments in other animals, and there is little difference between the response to condensation clicks and that to rarefaction clicks in this animal. However, when the duration of the click is increased or when broadband clicks are subjected to low-pass filtering, the intensity functions in response to condensation clicks do show a change in course, while the response to rarefaction clicks remains essentially unchanged. A similar change in the response to a broadband click can be induced by adding a low-pass-filtered click to the broadband click. The response to such a combination is not only a linear summation of the neural response to the individual components of the stimuli and the cochlear microphonics, but the low-frequency components that are added also affect the response to the broadband click, mainly by reducing the amplitude of the response.