Abstract
In contemporary cochlear implant systems, the audio signal is decomposed into different frequency bands, each assigned to one electrode. Thus, pitch perception is limited by the number of physical electrodes implanted into the cochlea and by the wide bandwidth assigned to each electrode. The Harmony HiResolution bionic ear (Advanced Bionics LLC, Valencia, CA, USA) has the capability of creating virtual spectral channels through simultaneous delivery of current to pairs of adjacent electrodes. By steering the locus of stimulation to sites between the electrodes, additional pitch percepts can be generated. Two new sound processing strategies based on current steering have been designed, SpecRes and SineEx. In a chronic trial, speech intelligibility, pitch perception, and subjective appreciation of sound were compared between the two current steering strategies and standard HiRes strategy in 9 adult Harmony users. There was considerable variability in benefit, and the mean results show similar performance with all three strategies.
Highlights
Cochlear implants are an accepted and effective treatment for restoring hearing sensation to people with severe-toprofound hearing loss
All subjects reported that speech experienced using Spectral Resolution Strategy (SpecRes) and SineEx was understandable immediately
The sound perceived with the new strategies was significantly different from High Resolution Strategy (HiRes) for some users
Summary
Cochlear implants are an accepted and effective treatment for restoring hearing sensation to people with severe-toprofound hearing loss. Contemporary cochlear implants consist of a microphone, a sound processor, a transmitter, a receiver, and an electrode array that is positioned inside the cochlea. The sound processor is responsible for decomposing the input audio signal into different frequency bands and delivering information about each frequency band to the appropriate electrode in a base-to-apex tonotopic pattern. The actual stimulation to each electrode consists of nonoverlapping biphasic charge-balanced pulses that are modulated by the lowpass-filtered output of each analysis filter. Most contemporary cochlear implants deliver interleaved pulses to the electrodes so that no electrodes are stimulated simultaneously. If electrodes are stimulated simultaneously, thereby overlapping in time, their electrical fields add and create undesirable interactions. Interleaved stimulation partially eliminates these undesired interactions. Research shows that strategies using nonsimultaneous stimulation achieve better performance than strategies using simultaneous stimulation of all electrodes [1]
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