The relationship between psychophysical and electrophysiological parameters in cochlear implantees

Electrophysiological measures with cochlear implantees provide objective information which may guide the clinician in the fitting of the device. They may also be used to measure objectively the effects of stimulation parameters such as pulse duration and interphase gap. The effects of these two parameters in psychophysical loudness studies have been proposed to be related to the degree of neural survival in the proximity of the activated electrode. Thus, if the two types of measures show the same effects, electrophysiological measures might be used to assess neural survival in implantees. In this paper, the effects of pulse duration changes on loudness and EABR amplitude are compared for four subjects (6 electrodes). The current reduction needed to maintain the same loudness when the pulse duration was doubled was compared to the current reduction required to achieve the same amplitude of EABR response. It is shown that these two measures are correlated, and that both measures show the same pattern of change with reference pulse duration.