Spectral and Temporal Analysis of Simulated Dead R

Authors: Jong Ho Won Gary L Jones Il Joon Moon Jay T Rubinstein

Publish Date: 2015/03/05

Volume: 16, Issue: 2, Pages: 285-307

PDF Link

Abstract

A cochlear implant CI electrode in a “cochlear dead region” will excite neighboring neural populations In previous research that simulated such dead regions stimulus information in the simulated dead region was either added to the immediately adjacent frequency regions or dropped entirely There was little difference in speech perception ability between the two conditions This may imply that there may be little benefit of ensuring that stimulus information on an electrode in a suspected cochlear dead region is transmitted Alternatively performance may be enhanced by a broader frequency redistribution rather than adding stimuli from the dead region to the edges In the current experiments cochlear dead regions were introduced by excluding selected CI electrodes or vocoder noisebands Participants were assessed for speech understanding as well as spectral and temporal sensitivities as a function of the size of simulated dead regions In one set of tests the normal input frequency range of the sound processor was distributed among the active electrodes in bands with approximately logarithmic spacing “redistributed” maps in the remaining tests information in simulated dead regions was dropped “dropped” maps Word recognition and Schroederphase discrimination performance which require both spectral and temporal sensitivities decreased as the size of simulated dead regions increased but the redistributed and dropped remappings showed similar performance in these two tasks Psychoacoustic experiments showed that the near match in word scores may reflect a tradeoff between spectral and temporal sensitivity spectralripple discrimination was substantially degraded in the redistributed condition relative to the dropped condition while performance in a temporal modulation detection task degraded in the dropped condition but remained constant in the redistributed conditionWe are grateful for the dedicated efforts of our cochlear implant and normalhearing subjects This research was supported by NIHNIDCD Grants F31DC009755 F32DC011431 R01DC007525 and P30DC04661 and the Advanced Bionics Corporation Il Joon Moon was supported by the Samsung Medical Center

Keywords: