Cochlear Implant

1. Cochlear Implant By: Sam Spink

2. What is it? • System of external and internal devices that aim to restore hearing to sensorineural hearing loss patients • Both pre- and post-lingual hearing loss • Does not restore functionality to natural cochlea; stimulates auditory nerve directly • Restored hearing is not exactly like natural hearing

3. Problem being solved • Sensorineural hearing loss • Most common form of hearing loss • Damage to either brain, auditory nerve, but most commonly sensory cells of cochlea (cochlear implant used for patients with this type) • 1.2 million Americans affected by hearing loss; sensorineural most common form • Functioning cochlea: vibrations cause fluid movement, which is sensed by hair cells of cochlea causing action potential firing to auditory nerve • These cells don’t function in those with cochlear implants

4. Current Technology • 5 major components • External devices: • Microphone-wraps around front of ear • Speech processor-behind ear; attached to microphone • Transmitter-above processor • Internal devices: • Receiver/stimulator-across from transmitter • Electrode array-placed on natural cochlea; wired to receiver

5. How it works • Microphone picks up sound, sends it to speech processor • Speech processor filters sound, converts to electrical signals through fast Fourier Transforms • Transmitter wirelessly sends signals to receiver/stimulator • Receiver/stimulator sends electrical current according to received signal to electrodes • Electrodes stimulate auditory nerve

6. Effectiveness • One study shows ability of cochlear implant recipients to identify sentences over telephone with 82 % success rate (pre-lingual) and 70% success rate (post-lingual) • With an adaptor increases to 93% and 88%, respectively • Speech development in children • For each 6 month period over first 30 months after receiving implant, subjects’ increase in “language age” was about double that of subjects without implants • Some performed at around same level as non-impaired

7. Limitations • Requires intense therapy post-implantation to achieve high level of speech comprehension (especially for post-lingual patients) • Device has trouble processing late echoing effects that go unnoticed by non-impaired ears • Costs between $45,000 and $125,000 • Surgical complications include infection, facial muscle weakness, facial paralysis, damaged vestibular system, loss of all residual hearing

8. Future Direction • Improvement in surgical techniques to keep residual hearing intact • If cure came about, patients would want what natural hearing still remained • Different electrode arrangements • Longer electrode arrays have shown potential to increase pitch range • Variations in electrode spacing at different points on the cochlea could improve sound quality

9. References • Hu, Y. and Kokkinakis, K. (2014). Effects of early and late reflections on intelligibility of reverberated speech by cochlear implant listeners. The Journal of the Acoustical Society of America, 135(1), pp.22--28. • Landsberger, D., Mertens, G., Punte, A. and Van De Heyning, P. (2014). Perceptual changes in place of stimulation with long cochlear implant electrode arrays. The Journal of the Acoustical Society of America, 135(2), pp.75--81. • Nidcd.nih.gov, (2014). Cochlear Implants. [online] Available at: http://www.nidcd.nih.gov/health/hearing/pages/coch.aspx [Accessed 27 Sep. 2014]. • Rigotti, P., Costa, O., Bevilacqua, M., Nascimento, L. and Alvarenga, K. (2013). Assessment of telephone speech perception in individuals who received cochlear implant in the period 1993-2003. 25(5), pp.400--406. • Svirsky, M., Robbins, A., Kirk, K., Pisoni, D. and Miyamoto, R. (2000). Language development in profoundly deaf children with cochlear implants. Psychological science, 11(2), pp.153--158. • Wikipedia, (2014). Cochlear implant. [online] Available at: http://en.wikipedia.org/wiki/Cochlear_implant [Accessed 27 Sep. 2014].