Survey of cochlear implant work

Abstract

The cochlear implant has recently seemed useful enough to be considered by some as a clinical procedure. This paper presents a review of the progress made on cochlear implants worldwide. Data are presented which contrast the results obtained in different labs on similar tests: threshold detection, pitch and loudness scaling, chronaxie, and difference limen tests. Models to account for some of these results are given. Four centers (San Francisco, Vienna, Salt Lake City, and Melbourne) have reported surprisingly good speech comprehension scores. We discuss the psychoacoustic characteristics which may relate to these scores and demonstrate that many implant patients show results which are expected quite typically in cochlear dysfunction. Thus the limits on speech processing in the hard-of-hearing may apply as well to implant patients, regardless of the method of speech coding. We also stress the lack of evidence confirming the assumed greater usefulness of multi-channel implants over single channel devices. Finally, a careful look is given to the risks involved in these procedures, specifically those of bone and tumor growth, device replacement, and the psychological effects from device failure.