Forward masking patterns and pitch estimation for bipolar and remote ground stimulation in a subject implanted with a Cochlear Pty. Limited ‘‘20+2’’ cochlear implant

Abstract

A new electrode array, recently developed by Cochlear Pty. Limited, enables ‘‘remote ground’’ as well as standard bipolar stimulation. To compare the patterns of electrical stimulation for these two operating modes, forward masking and pitch estimation investigations were performed with a single patient. The masking patterns were studied using a bipolar+1 or a remote ground masker, followed by a bipolar+1 probe. For maskers on apical and middle electrodes, masking patterns were more apical for bipolar +1 than for remote ground maskers, while for maskers on a basal electrode, masking was similar for the two masker modes. For a bipolar+1 masker on a middle electrode, masking was skewed strongly toward the apical end of the array. In the apical half of the array, while remote ground pitch reduced regularly with movement apically, bipolar+1 pitch dropped abruptly to a constant low value for the nine most apical electrodes and was lower than remote ground pitch for each electrode. The results show that remote ground stimulation may provide a different, and at least for this patient a better, range of pitch percepts, as well as other benefits such as reduced current requirement. [Work supported by NIH.]