Personal reflections on the multichannel cochlear implant and a view of the future

Abstract

Abstract-The multichannel cochlear implant is the first neural prosthesis to effectively and safely bring electronic technology into a direct physiological relation with the central nervous system and human consciousness. It is also the first cochlear implant to give speech understanding to tens of thousands of persons with profound deafness and spoken language to children born deaf in more than 80 countries. In so doing, it is the first major advance in research and technology to help deaf children communicate since Sign Language of the Deaf was developed at the Paris deaf school (L'Institut National de Jeunes Sourds de Paris) >200 years ago. Furthermore, biomedical research has been fundamental for ensuring that the multielectrode implant is safe as well as effective. More recent research has also shown that bilateral implants confer the benefits of binaural hearing. Future research using nanotechnology should see high-fidelity sound received, which would help deaf persons communicate in noise and enjoy music. Research should also lead to implants in ears with useful hearing.Key words: audiology, auditory neurophysiology, auditory psychophysics, bioengineering, education of hearing impaired, multichannel cochlear implant, nanotechnology, neural prosthesis, rehabilitation, severe to profound deafness, speech science. PERSONAL REFLECTIONS Hearing from Electrical Stimulation of Auditory Nerve Preliminary Studies on Subjects with HearingInterest in electrical methods of inducing hearing started after Alessandro Volta, who discovered the electrolytic cell, stimulated his own auditory system by connecting a battery of 30 or 40 "couples" to two metal rods, which he inserted into his ears. The sensation was momentary and lacked tonal quality [1].Because sound is an alternating disturbance in an elastic medium, stimulating the auditory system with a direct current (DC) was later appreciated to not reproduce a satisfactory hearing sensation. Consequently, Duchene of Boulogne in 1855 [2], and later others, stimulated the ear with an alternating current. The result, however, was still not satisfactory, and only noise was produced.Renewed interest occurred with the introduction of the thermionic valve, which enabled the auditory system to be stimulated electrically with much greater precision. This work was supported by the findings that the voltages recorded from the auditory nerve of a cat were similar in frequency and amplitude to the sounds presented to the ear, but they were still heard as noise [3].Abbreviations: ABF = adaptive beamformer, ACE = Advanced Combination Encoder, ADRO = adaptive dynamic range optimization, AGC = automatic gain control, ARC = Australian Research Council, ASC = automatic sensitivity control, CIS = continuous interleaved sampling, CNC = consonant-nucleusconsonant, DC = direct current, DRSP = differential rate speech processor, F0 = fundamental (voicing) frequency, F1 = first formant frequency, F2 = second formant frequency, FDA = Food and Drug Administration, NIH = National Institutes of Hea...

Directing neuronal cell growth on implant material surfaces by microstructuring

“…[3][4][5] It consists of an array of maximal 22 platinum electrode contacts embedded in insulating silicone. This limited number of electrode contacts takes over the task of the IHC and the frequency discrimination is accordingly poor compared to the natural hearing sensation.…”

Hearing restoration: Graeme Clark, Ingeborg Hochmair, and Blake Wilson receive the 2013 Lasker~DeBakey Clinical Medical Research Award

“…He soon left his position at the Royal Victorian Eye and Ear Hospital to pursue a PhD in neurophysiology. His dissertation research focused on the role of the middle ear structure in transmitting sound and the responses in the brain (10,11). Much of Clark's early research was done in a cat model.…”

The multi-channel cochlear implant: Multi-disciplinary development of electrical stimulation of the cochlea and the resulting clinical benefit

“…The idea of electrically stimulating the auditory nerves to restore hearing in severely-profoundly deaf people emerged in the early 20th century with experimental studies in centres in Europe, the US, and Australia, as discussed (Clark, 2001(Clark, , 2003b(Clark, , 2008. But many scientists said speech understanding would not be possible (Lawrence, 1964) as the neural network in the cochlea for the initial encoding of sound was too complex.…”

“…Nevertheless, I reasoned the question should be answered with multi-disciplinary research to show what the limits for the coding of speech were. This required convergent research in surgical anatomy and pathology, neurobiology, neurophysiology, psychophysics, speech science, communications and bioengineering, audiology and speech pathology, otology, and (re)habilitation (Clark, 2006(Clark, , 2008(Clark, , 2013. My research, commencing in 1967, was initially undertaken to answer the basic question could electrical stimulation reproduce the coding of frequency and intensity?…”