Abstract
Amplitude modulation (AM) detection performance has been studied in the past with normal-hearing and hearing-impaired populations. The temporal modulation transfer function (TMTF) is a plot of AM detection performance as a function of modulation rate and provides a way of characterizing temporal sensitivity. Typically the TMTF takes the form of a low-pass filter, with performance declining above 50–70-Hz modulation rate. TMTFs have also been measured with cochlear implant patients, showing a similar low-pass characteristic, with a cutoff around 140-Hz rate, while sensitivity to AM was found to increase with increasing current level. The present study investigated the effects of stimulation level and electrode separation on TMTFs with cochlear implant patients. TMTFs were measured for narrow through wide electrode separations and three different (loudness-balanced) percentages of the dynamic range. Preliminary results indicate that sensitivity increases (lower thresholds) with increasing stimulation level, for a given electrode separation. However, comparing TMTFs across different electrode separations, sensitivity is independent of current level, but increases as a function of percentage of dynamic range. In summary, it appears that AM detection performance with cochlear implants depends primarily on sensation level, rather than current level or electrode separation. [Work supported by NIDCD Grant No. R01DC04786.]
Published Version
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