Implementation of a microprocessor-based tactile hearing prosthesis.

A significant number of deaf patients that have received cochlear implants now achieve higher word recognition scores then those with conventional auditory prostheses. This situation makes the choice of which type of auditory rehabilitation to propose a complex matter in patients with remaining auditory function. Our paper aims at providing some arguments to these new questions by presenting the clinical experience and practice of the Centre romand d'implants cochléaires. We also address related legal issues. Clinical tools, such as testing the comprehension of lists of logatoms have proved very useful for the evaluation of these particular patients. The evaluation of cochlear implant candidates remains a highly individualized process, necessitating a case by case approach by an experienced multidisciplinary cochlear implant team.

Cochlear Implants↗

PubMed2006

Indication for the need of flexible and frequency specific mapping functions in cochlear implant speech processors.

Categorical loudness scaling of electric and acoustic stimuli was performed in cochlear implant (CI) recipients equipped with Nucleus systems in order to achieve a normal loudness perception in the whole dynamic range of acoustic input. For each electrode, the lower and upper limits of electric stimulus were defined by the values corresponding to "very soft" and "too loud". Within this dynamic range, the stimulus strength intervals associated to the verbal categories "soft", "medium", "loud" and "very loud" were determined. The same loudness categories were used for the scaling of acoustic stimuli. From both scaling experiments, the transduction of the CI system can be assessed and the parameters of the individual mapping function yielding a normal loudness growth can be derived. Deviations from optimum mapping can be corrected at least partially by manipulating the parameters of the mapping function. In many cases, however, one mapping function is not sufficient for all channels. The results argue in favour of the development of flexible and channel-specific mapping function parameters in future CI systems.

Cochlear Implants↗

PubMed2006

The multiple-channel cochlear implant: the interface between sound and the central nervous system for hearing, speech, and language in deaf people-a personal perspective.

The multiple-channel cochlear implant is the first sensori-neural prosthesis to effectively and safely bring electronic technology into a direct physiological relation with the central nervous system and human consciousness, and to give speech perception to severely-profoundly deaf people and spoken language to children. Research showed that the place and temporal coding of sound frequencies could be partly replicated by multiple-channel stimulation of the auditory nerve. This required safety studies on how to prevent the effects to the cochlea of trauma, electrical stimuli, biomaterials and middle ear infection. The mechanical properties of an array and mode of stimulation for the place coding of speech frequencies were determined. A fully implantable receiver-stimulator was developed, as well as the procedures for the clinical assessment of deaf people, and the surgical placement of the device. The perception of electrically coded sounds was determined, and a speech processing strategy discovered that enabled late-deafened adults to comprehend running speech. The brain processing systems for patterns of electrical stimuli reproducing speech were elucidated. The research was developed industrially, and improvements in speech processing made through presenting additional speech frequencies by place coding. Finally, the importance of the multiple-channel cochlear implant for early deafened children was established.

Cochlear Implants↗