Relation of Psychophysical Data to Histopathology in Monkeys with Cochlear Implants

TLDR

Psychophysical measures of threshold and dynamic range for electrical stimulation were obtained in macaque monkeys with scala tympani electrodes, followed by postmortem examination of cochleas and brain stem. Low thresholds and large dynamic ranges correlated with minimal organ of Corti damage and brain stem degeneration, whereas high thresholds and small dynamic ranges were associated with extensive sensorineural cochlear damage and brain stem degeneration, and implant orientation had little effect on threshold.

Abstract

Psychophysical measures of threshold and dynamic range for electrical stimulation were made in macaque monkeys that had electrodes implanted in the scala tympani. At the completion of psychophysical testing the monkeys were sacrificed and the cochleas and brain steins examined. Low thresholds and large dynamic ranges were associated with minimal damage to the organ of Corti and minimal brain stem degeneration. whereas thresholds were high and dynamic ranges small in subjects showing a high degree of sensorineural cochlear damage and brain stem degeneration. Three different implant orientations were observed. but orientation did not seem to have a major effect on threshold.