Cochlear Implants: System Design, Integration, and Evaluation

Abstract

As the most successful neural prosthesis, cochlear implants have provided partial hearing to more than 120,000 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 from design and specifications to integration and evaluation. 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.

Effects of Brain-Derived Neurotrophic Factor (BDNF) and Electrical Stimulation on Survival and Function of Cochlear Spiral Ganglion Neurons in Deafened, Developing Cats

“…On average, CI users with the latest technology enjoy speech recognition scores of about 80 % correct on high-context sentences, the majority are able to use a telephone (Zeng et al 2008), and those with the best outcomes even enjoy music (Drennan and Rubinstein 2008;Won et al 2011). However, results on more difficult tasks such as word recognition show that there is great variability among CI recipients (Firszt et al 2004;Holden et al 2013).…”

Implantes cocleares: aspectos tecnológicos e papel socioeconômico

“…Este algoritmo calcula uma média móvel da amplitude do sinal para extrair a energia em cada banda, podendo ser realizado por retificação seguida de filtragem passa-baixas ou pela Transformada de Hilbert (Lorens et al, 2010;Zeng et al, 2008).…”

“…A taxa de pulsos é tipicamente maior que 800 pulsos por segundo (pps) por eletrodo (Wilson et al, 1993). A hipótese de que acréscimo na taxa de pulsos pudesse melhorar o entendimento devido à maior definição temporal não se mostrou verdadeira (Loizou, 1998;Zeng et al, 2008). Isso se deve ao fato de que, após receberem um estímulo, as fibras nervosas precisam de um intervalo para se repolarizarem, chamado de período refratário (Clark et al, 1977).…”

“…Além disso, a faixa dinâmica varia de acordo com a frequência. Para condicionar o sinal útil entre o limiar de percepção e o nível de audição confortável, é necessário aplicar um ganho não-linear a cada banda de acordo com a necessidade do paciente (Zeng et al, 2008). Esse procedimento é chamado de compressão do sinal e, em resumo, significa a amplificação de sons de baixa intensidade e a atenuação de sons de alta intensidade.…”

Assessment and improvement of sound quality in cochlear implant users

“…Unfortunately, fine structure processing (FSP) has not been incorporated into the majority of current processing strategies. Continuous interleaved sampling (CIS), currently fundamental to processing strategies offered by all CI manufacturers, interleaves biphasic pulse trains so that no two pulses occur simultaneously 32. While this has helped mitigate channel interaction, CIS transmits only envelope information via fast fixed rate electrode stimulation and discards fine structure entirely.…”