Design of the Cochlear Prosthesis: Effects of the Flow of Current in the Implanted Ear

Abstract

When structures within the temporal bone are stimulated electrically it is desirable to maximize the dynamic range of the stimulus. The maximum dynamic range of electrical stimulus seems to be found when the threshold of stimulation is minimum. The minimum threshold of stimulus is likely to be reached when the electrical current that flows through regions containing excitable cells is maximized. By implanting electrodes throughout the temporal bone, it is possible to apply electrical currents to the ear and to measure the distributions of current flowing within the ear. The results of these measurements demonstrate that when current flow is directed outside the scala tympani, lower thresholds can be obtained. Frequency dependence of the paths of current flow canot be used to explain the frequency dependence of the frequency-threshold functions measured in animals.

Keywords

Cochlear prosthesis electrical stimuli electrical current frequency guinea pig

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