Current Distribution Measurements Within the Human Cochlea

The magnitudes of the currents returned through each ground electrode line of a multiple-electrode cochlear implant array were determined during surgical implantations on two patients. These were often found to be distributed widely to points far from the stimulus electrode site. Further measurements made in in vitro solutions demonstrated that the distributions were due largely to the ground electrode interface impedances being significantly larger than the fluidpath impedances, and demonstrated that distributions could be changed by modification of the ground electrode interface impedances.