The Sound Sensation of Apical Electric Stimulation in Cochlear Implant Recipients with Contralateral Residual Hearing

Abstract

BackgroundStudies using vocoders as acoustic simulators of cochlear implants have generally focused on simulation of speech understanding, gender recognition, or music appreciation. The aim of the present experiment was to study the auditory sensation perceived by cochlear implant (CI) recipients with steady electrical stimulation on the most-apical electrode.Methodology/Principal FindingsFive unilateral CI users with contralateral residual hearing were asked to vary the parameters of an acoustic signal played to the non-implanted ear, in order to match its sensation to that of the electric stimulus. They also provided a rating of similarity between each acoustic sound they selected and the electric stimulus. On average across subjects, the sound rated as most similar was a complex signal with a concentration of energy around 523 Hz. This sound was inharmonic in 3 out of 5 subjects with a moderate, progressive increase in the spacing between the frequency components.Conclusions/SignificanceFor these subjects, the sound sensation created by steady electric stimulation on the most-apical electrode was neither a white noise nor a pure tone, but a complex signal with a progressive increase in the spacing between the frequency components in 3 out of 5 subjects. Knowing whether the inharmonic nature of the sound was related to the fact that the non-implanted ear was impaired has to be explored in single-sided deafened patients with a contralateral CI. These results may be used in the future to better understand peripheral and central auditory processing in relation to cochlear implants.

Faster phonological processing and right occipito-temporal coupling in deaf adults signal poor cochlear implant outcome

“…On the one hand, auditory recovery with a CI relies on the availability of the visual cortex in the post-implantation phase, because the latter permits the remapping between visemes (lip movements) and perceived phonemes567. Auditory input from the CI is crude43 and patients must learn the fine correspondence between these new acoustic patterns and previously learned speech sound representations1844. On the other hand, enhanced involvement of the right temporal lobe in speech processing, which occurs during deafness918 and persists after implantation678, seems detrimental to auditory recovery.…”

Multidimensional scaling between acoustic and electric stimuli in cochlear implant users with contralateral hearing

“…If the perceptual difference represented by dimension 2 is based on the “buzzy” or “noisy” percept of monopolar stimulation, then a repetition of this experiment using monopolar and current focused stimulation should reveal that current focused pulse trains are perceptually more similar to the acoustic stimulation than the monopolar stimuli. Lazard et al (2012) asked patients to adjust the width of bandpass filtered noise presented to an ear with residual low-frequency hearing to provide the best match to a fixed rate pulse train on the most apical electrode of a Cochlear Nucleus device. The bandwidth representing the best acoustic match varied greatly across subjects.…”

The role of the Utah Artificial Ear project in the development of the modern cochlear implant

“…The fuzziness of the percept interfered with his ability to match the pitch of electrical stimulation with stimulation directed to the other, acoustically sensitive, ear. This report presages the many problems experienced in recent years with attempts to match the 'fuzzy' pitch of electric stimulation to that of acoustic stimulation in bimodal and singlesided deaf CI patients (e.g., Dorman et al, 1994;Lazard et al, 2012; see also Spahr et al, 2008, for experiments on melody recognition by normal hearing listeners using simulations of 'fuzzy' pitch. ).…”