The multichannel cochlear implant for severe-to-profound hearing loss

Abstract

At a glance Figures View all figures Figure 1: Graeme Clark with his father, Colin, at age 90. Full size image View in article Figure 2: Temporal and place coding of sound. In temporal coding, neurons fire action potentials in phase with the sound waves (left). Place coding (right) refers to the perception of pitch depending on the site of stimulation. This is possible because the brain centers that respond to sound are arranged tonotopically—cells located at different sites along the auditory system respond to different sound frequencies in a highly organized fashion that is projected in an identical pattern through the pathway, from the cochlea to the cerebral cortex. Full size image View in article Figure 3: Graeme Clark, with a diagram of the cochlea, explaining his proposed research when appointed in 1970 as the University of Melbourne's first William Gibson Chair of Otolaryngology, situated at the Royal Victorian Eye & Ear Hospital. Full size image View in article Figure 4: Early implants. (a) Jim Patrick and Ian Forster with the silicon chip design for the first multichannel implant developed in the Department of Otolaryngology, University of Melbourne, 1977. (b) Communicating with Rodney Saunders—Graeme Clark's first patient—in 1978. (c) The completion of the first multichannel implant operation at the Royal Victorian Eye & Ear Hospital by the leaders of the University of Melbourne's surgical team, Graeme Clark and Brian Pyman, with the receiver-stimulator placed in its bed. Full size image View in article Figure 5: Psychophysical studies in the first patient. (a) Pitch versus rate and place of stimulation. The pitch increased from 50 pulses/s to 200 pulses/s and then reached a plateau. It also increased with place of stimulation from apical (#1) to basal (#8) electrodes. (b) Timbre and place of stimulation related to the vowels' second formant (F2). The vowels like /e/ and /i/ originated from high-frequency regions, were perceived as sharp and had high second formants. Vowels like /o/ originated from low-frequency regions around the outside of the auditory nerve due to extra-cochlear current spread, were dull and had low second formants. (c) The speech feature/formant (F0/F2)-based speech code. For the word /wit/ the first (F1), second (F2) and third (F3) formants over time are the continuous lines. Our successful inaugural feature extraction speech code is illustrated by the vertical bars that are the electrical pulses. The F2 was extracted as it conveys most intelligibility. For /w/, as the F2 increases in frequency, the site of stimulation moves upward; for the vowel /i/ it is steady; and for /t/ it stimulates a high-frequency site. The pulse rate is proportional to the voicing frequency, and for the noise in /t/ it is random. Full size image View in article Figure 6: Other important milestones. (a) Graeme Clark's second patient, George Watson, wearing a speech processor and speaking with senior audiologist Lois Martin, 1979. (b) First Nucleus (Cochlear Ltd.) multichannel cochlear implant for clinical trial, 1982. (c) Peter Stewart, the first adult to have a bilateral cochlear implant. (d) The first children to receive the multichannel cochlear implant. (e) Sian Neame, our first young child with the implant, in 1990 at 2.5 years old. (f) Sian meeting Her Majesty Queen Elizabeth II in 2000 during a visit to the Bionic Ear Institute at the University of Melbourne. Full size image View in article