High Frequency Evoked Action Potentials Recorded from the Ear Canal in Man

Abstract

The present experiment outlines the properties of human APs evoked by high frequency (8 kHz) clicks and recorded from the ear canal in normals. The input-output functions for the AP are established and compared with the corresponding 2 kHz functions: The two latency functions coincide at high-but diverge significantly at low intensities. The two amplitude functions have almost identical maximum values at the highest intensity, but the 8 kHz function is more gradual than the 2 kHz function. It is concluded that at high intensities the two stimuli are equally effective in their excitation of the basal part of the cochlea and that the APs are generated mainly from this area. At low intensities the excitation patterns differ and the two stimuli generate APs originating from different and specific parts of the cochlea. Based on data on single auditory nerve fibres, i.e. tuning curves and rate functions, a qualitative AP-parameter model is proposed and used for the description of the findings.