With commonly used monopolar or __single electrode stimulation__ (SES) in cochlear implants the perceived pitch depends on the place in the cochlea of the stimulated contact. When two contacts are... Show moreWith commonly used monopolar or __single electrode stimulation__ (SES) in cochlear implants the perceived pitch depends on the place in the cochlea of the stimulated contact. When two contacts are stimulated simultaneously, __dual electrode stimulation__(DES), intermediate pitches can be elicited. The place and precise pitch can be adjusted by varying the current ratio between these two contacts. In this thesis the mechanism of DES is investigated psychophysically, electrophysiologically and in a computational model of the cochlea. It was concluded that DES and SES are indistinguishable in terms of spread of excitation and sequential channel interaction, while with DES the pitch depends linearly on the current ratio. On adjacent contacts, DES turned out to be effective for the entire dynamic range without the need for any current correction to equalize loudness between pitches. DES is also feasible on non-adjacent contacts (__spanning__) up till 4.4 mm, but with increasing distance between the contacts, such a current correction becomes mandatory, while also the number of discriminable pitches decreases. Finally, spanning was implemented in a speech coding strategy and tested in a take-home trial, which demonstrated that even with two groups of three adjacent defective contacts, speech perception and sound quality were retained. Show less
