Cochlear Implants: System Design, Integration, and Evaluation

Depts. of Anatomy & Neurobiol., Univ. of California, Irvine, CA
IEEE Reviews in Biomedical Engineering 02/2008; 1(1):115 - 142. DOI: 10.1109/RBME.2008.2008250
Source: IEEE Xplore


As the most successful neural prosthesis, cochlear implants have provided partial hearing to more than 120000 persons worldwide; half of which being pediatric users who are able to develop nearly normal language. Biomedical engineers have played a central role in the design, integration and evaluation of the cochlear implant system, but the overall success is a result of collaborative work with physiologists, psychologists, physicians, educators, and entrepreneurs. This review presents broad yet in-depth academic and industrial perspectives on the underlying research and ongoing development of cochlear implants. The introduction accounts for major events and advances in cochlear implants, including dynamic interplays among engineers, scientists, physicians, and policy makers. The review takes a system approach to address critical issues in cochlear implant research and development. First, the cochlear implant system design and specifications are laid out. Second, the design goals, principles, and methods of the subsystem components are identified from the external speech processor and radio frequency transmission link to the internal receiver, stimulator and electrode arrays. Third, system integration and functional evaluation are presented with respect to safety, reliability, and challenges facing the present and future cochlear implant designers and users. Finally, issues beyond cochlear implants are discussed to address treatment options for the entire spectrum of hearing impairment as well as to use the cochlear implant as a model to design and evaluate other similar neural prostheses such as vestibular and retinal implants.

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Available from: Haihong Feng, Oct 13, 2014
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    • "al reasons why adolescents using CIs may not have developed specialized auditory cortices similar to their normal hearing peers . They had been bilaterally deaf from early in life ( typically from birth ) and listened , often unilaterally , to a representation of sound missing much of its fine temporal information [ Drennan and Rubinstein , 2008 ; Zeng et al . , 2008 ] . It is possible that specialization has not yet emerged in these pathways , with contralateral afferent projections still dominating auditory input as in earlier development [ Gordon et al . , 2013a , b ] . Effects of unilateral auditory depri - vation / stimulation appear to occur early and persist into maturation . In younger child"
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    ABSTRACT: Unilateral cochlear implant (CI) stimulation establishes hearing to children who are deaf but compromises bilateral auditory development if a second implant is not provided within ∼1.5 years. In this study we asked: 1) What are the cortical consequences of missing this early sensitive period once children reach adolescence? 2) What are the effects of unilateral deprivation on the pathways from the opposite ear? Cortical responses were recorded from 64-cephalic electrodes within the first week of bilateral CI activation in 34 adolescents who had over 10 years of unilateral right CI experience and in 16 normal hearing peers. Cortical activation underlying the evoked peaks was localized to areas of the brain using beamformer imaging. The first CI evoked activity which was more strongly lateralized to the contralateral left hemisphere than normal, with abnormal recruitment of the left prefrontal cortex (involved in cognition/attention), left temporo-parietal-occipital junction (multi-modal integration), and right precuneus (visual processing) region. CI stimulation in the opposite deprived ear evoked atypical cortical responses with abnormally large and widespread dipole activity across the cortex. Thus, using a unilateral CI to hear beyond the period of cortical maturation causes lasting asymmetries in the auditory system, requires recruitment of additional cortical areas to support hearing, and does little to protect the unstimulated pathways from effects of auditory deprivation. The persistence of this reorganization into maturity could signal a closing of a sensitive period for promoting auditory development on the deprived side. Hum Brain Mapp, 2015. © 2015 Wiley Periodicals, Inc.
    Human Brain Mapping 10/2015; DOI:10.1002/hbm.23019 · 5.97 Impact Factor
    • "As a highly successful neural prostheses, cochlear implant have been used for many years to help patients who suffer from sensorineural hearing loss recover the sense of hearing. The cochlear implant works by directly stimulating the residual auditory nerve fibers inside the cochlea according to their naturally developed tonotopic organization [1], [2]. Despite the significant improvements that have been made in the past decades, the performance of modern cochlear implants is still far behind the healthy cochlea. "
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    • "By the late 1980s, steps 1 and 2 had been achieved and step 3 had been largely achieved (Wilson and Dorman, 2008a; Zeng et al., 2008). Both single-site and multisite systems were being applied clinically. "
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    ABSTRACT: The challenge in getting a decent signal to the brain for users of cochlear implants (CIs) is described. A breakthrough occurred in 1989 that later enabled most users to understand conversational speech with their restored hearing alone. Subsequent developments included stimulation in addition to that provided with a unilateral CI, either with electrical stimulation on both sides or with acoustic stimulation in combination with a unilateral CI, the latter for persons with residual hearing at low frequencies in either or both ears. Both types of adjunctive stimulation produced further improvements in performance for substantial fractions of patients. Today, the CI and related hearing prostheses are the standard of care for profoundly deaf persons and ever-increasing indications are now allowing persons with less severe losses to benefit from these marvelous technologies. The steps in achieving the present levels of performance are traced, and some possibilities for further improvements are mentioned. Copyright © 2014. Published by Elsevier B.V.
    Hearing Research 12/2014; 322. DOI:10.1016/j.heares.2014.11.009 · 2.97 Impact Factor
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