title: Auditory evoked potentials to continuous amplitude-modulated sounds: can they be described by linear models?
abstract: The responses from the round window of the cochlea and the surface of the cochlear nucleus to continuous tones and noise that were amplitude-modulated with pseudorandom noise were studied. The responses were averaged with the averager locked to the periodicity of the pseudorandom noise, and the cross-correlation between the averaged responses and one period of the pseudorandom noise was computed. The degrees of non-linearities in the responses were estimated by comparing the response of a linear model that had this cross-correlogram as its impulse response and the physiological response. The root mean square (RMS) value of the histograms increases as a function of the stimulus intensity and reaches a peak at 40-60 dB above threshold, above which intensity it decreases. The non-linear component of the response increases monotonically with sound intensity in the range from threshold to 60-70 dB above threshold. The pseudorandom noise was of the inverse-repeat type, and when even-order non-linearities were canceled by subtracting the latter half of the responses to one period of the pseudorandom noise from the first half a much closer agreement with the model responses was obtained, indicating that the non-linearities were mainly of even order. It was concluded that the non-linearities of the responses may have been caused by an unequal response to increases and decreases in stimulus intensity.
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000818:Animals; D005072:Evoked Potentials, Auditory; D008959:Models, Neurological; D009622:Noise; D051381:Rats; D011919:Rats, Inbred Strains; D012249:Rhombencephalon / Q000502:physiology*; D012405:Round Window, Ear / Q000502:physiology