Neural excitation patterns induced by phased-array stimulation in the implanted human cochlea

Conclusions: Phased-array stimulation is a promising technique, which uses electrical interaction to focus the stimulation in cochlear implants, at the expense of limited threshold shifts. It has potential advantages over, for example, tripolar stimulation. Objectives: Current spread imposes limitations in cochlear implants. Van Compernolle (1985) suggested using all electrode contacts simultaneously to reduce these effects. Van den Honert et al. (2007) validated this so-called phased array algorithm in patients with respect to the electrode potentials but the effect on neural excitation remained unclear. The present study used computational modeling to relate the effect of phased-array stimulation to the neural elements. Methods: A computational model of the implanted human cochlea was used to compare the neural excitation patterns induced by conventional monopolar stimulation and by phased-array stimulation. Neural thresholds and electrical dynamic ranges were visualized with excitation profiles, showing the auditory nerve's response to a range of stimulus levels. Results: Phased-array stimulation of a single region reduces the spread of excitation and increases the dynamic range. The phased array paradigm can be extended to stimulate multiple sites simultaneously, thereby eliminating the need for sequential stimulation, but with a more limited range of usable stimulus levels, especially with perimodiolar electrodes.