Analysis of compound action potential responses to tone bursts in the human and guinea pig cochlea

Abstract

In electrococholegraphy, compound action potentials (AP) are recorded from the human promontory and the guinea pig round window. High-pass noise masking and subtraction of AP responses at various high-pass cutoff frequencies give the narrow-band contributions to the whole nerve AP. Although the narrow-band contributions recorded from human and guinea pig ears differ essentially, this narrow-band concept makes it possible to derive a response area for a given type of stimulus, e.g., tone bursts. Within the response area, any combination of stimulus intensity and site on the cochlear partition evokes a detectable narrow-band response contributing to the whole-nerve AP. The main part of this contribution shifts basally the higher the stimulus intensity. Latency differences between responses from the various narrow bands are used to calcuate the traveling-wave velocity for the human cochlea, which ranges from about 20 m/sec at 10 kHz to 1 m/sec at 500 Hz. The amplitude and width of the narrow-band responses are closely related to the traveling-wave velocity in the narrow band. It is argued that the response area and the narrow-band-response concept offer a means to relate electrocochleography in the human subject to the results obtained from single-fiber studies in the normal and pathological animal cochlea. Subject Classification: [43]65.26, [43]65.20, [43]65.22, [43]65.40.