Channel interactions measured by forward‐masked “place” tuning curves with multichannel electrical stimulation

Abstract

Simultaneous stimulation of multichannel intracochlear electrodes can give rise to peripheral and central channel interactions. The ability to eliminate or predict and control the interactions produced by a given electrode geometry is a processing goal for optimizing performance with a multichannel cochlear implant. Previous studies have used loudness summation and forward‐masking pattern techniques to estimate interactions between channels of electrical stimulation. In this study, interactions between bipolar channels of analog electrical stimulation were estimated using a forward‐masking paradigm with a fixed‐level, fixed‐location probe. By varying the electrode location of a 200‐Hz, 300‐ms sinusoidal masker and determining the level of the masker at each location necessary to just mask a 200‐Hz, 10‐ms probe, a “place” tuning curve was derived. The level of masker required at a given location to mask the probe depends on the amount of excitation produced by the probe and reflects, in part, the degree to which there is overlap of neural populations responding to each stimulus. These “place” tuning curves, which display interactions as a function of masker location were determined for several probe levels and probe locations. Results and implications for speech processing strategies will be discussed.