Frequency nonlinearity in sustained auditory evoked potentials

Document Type

Article

Publication Date

1993

Publication Title

Chinese Journal of Biomedical Engineering

Volume

12

Issue

3

First Page

203

Last Page

209

Abstract

In this paper, properties of responses to periodic stimuli of some biological systems was studied, in which the sustained response could reach steady state if the duration of the stimulus is long enough. It was shown that the steady state components of the sustained response f(n)(t) could be expressed by the summation of the waveforms obtained by shifting a fully masked response to a single cycle u(n)(t) within the stimulus with intervals equal to the integer times of the cycle. It has been pointed out that the spectra of f(a)(t) and u(n)(t) could be correlated with the following formula: [F(n)(ω)] = [U(n)(ω)](sin(n + 1)ωT/sinωT], where T stands for the cycle of the stimulus. From this formula, it was deduced that there would be peaks in the spectrum of the steady state response as the frequencies equaled to the integer times of the frequency of the stimulus, the higher the frequency of the stimulus, the less would be the harmonic components, and the frequency range of the steady state response was restricted by the frequency pass band of [U(n)(ω)]. These conclusions were tested and verified in chochlea potentials and brainstem auditory potentials, the cochlea potentials being recorded from the round window of inner ear of guinea pigs and the brainstem auditory potentials from the scalp. A comparison of the theoretical expectant and experimental results was also made quantitatively. The well fitting result was a strong support to our theory and gave a reasonable explanation to the 'frequency following' mechanism and the frequency nonlinearity phenomenon in biological systems, which was rather general for evoked potentials. Besides, a possible explanation was also given for the frequency limitation of auditory frequency following responses. Properties of responses to periodic stimuli of some biological systems were studied, in which the sustained response can reach steady state if the duration of the stimulus is long enough. It was shown that the steady state component of the sustained response fn(t) can be expressed by the summation of the waveforms obtained by shifting a fully masked response to a single cycle un(t) within the stimulus with intervals equal to the integer times of the cycle. It has been pointed out that the spectra of fn(t) and un(t) can be correlated with a formula. From the formula, it was deduced that there would be peaks in the spectrum of the frequency of the stimulus; the higher the frequency of the stimulus, the less would be the harmonic components; and the frequency range of the steady state response was restricted by the frequency pass band of ∥Un(ω)∥. These conclusions were tested and verified in cochlea potentials and brain stem auditory potentials, the cochlea potentials being recorded from the round window of inner ear of guinea pigs and the brain stem auditory potentials from the scalp.

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