Bipolar stimulation has been thought to be more beneficial than monopolar stimulation for speech coding in cochlear implants, on the basis of its more restricted current flow. The present study examined whether bipolar stimulation would indeed lead to reduced channel interaction in a behavioral forward masking experiment tested in four Nucleus 24 users. The masker was fixed on one channel and three masker levels that were balanced for loudness between the configurations were chosen. As expected, masking was maximal when the masker and probe channels were spatially close and decreased as they were separated. However, overall masking patterns did not consistently demonstrate sharper tuning with bipolar stimulation than monopolar. This implies that the spatial extent of a bipolar current field is not consistently narrower than that of an equally loud monopolar stimulus; therefore, it should not be assumed that bipolar stimulation leads to reduced channel interaction. Notably, bipolar masking patterns appeared to display more variations across channels, possibly influenced more by anatomical and neural irregularities near electrode contacts than monopolar masking patterns. The present psychophysical results provide a theoretical basis regarding the widespread use (and success) of monopolar configurations by implant users.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.