This Article 
 Bibliographic References 
 Add to: 
A Cochlear-Implant Processor for Encoding Music and Lowering Stimulation Power
January-March 2008 (vol. 7 no. 1)
pp. 40-48
Ji-Jon Sit, Advanced Bionics
Rahul Sarpeshkar, Massachusetts Institute of Technology
This 75 dB, 357 mW analog cochlear-implant processor encodes fine-phase-timing spectral information in its asynchronous stimulation outputs, to convey music to deaf patients. This processor features asynchronous interleaved sampling (AIS) and uses a race-to-spike winner-take-all strategy. This strategy ensures that sampling for electrode stimulation occurs on only one channel at a time, thus preventing electrode-smearing interactions. Phase-encoded, high-rate sampling of high-intensity channels, along with lower-rate sampling of low-intensity channels, is typically achievable. This keeps stimulation power low and enables more natural, asynchronous stochastic stimulation of the auditory nerve. Reconstructions of music encoded from this processor’s sampled outputs reveal significantly better fidelity compared with traditional processing schemes, which convey only amplitude information. This processor’s power consumption is more than an order of magnitude lower than traditional A/D-then-DSP cochlear-implant processors. Programmability is achievable because 546 bits can alter 165 spectral and AIS parameters via a serial interface. This article is part of a special issue on implantable electronics.

1. P.C. Loizou, "Mimicking the Human Ear," IEEE Signal Processing Magazine, vol. 15, no. 5, 1998, pp. 101–130.
2. J.W. Picone, "Signal Modeling Techniques in Speech Recognition," Proc. IEEE, vol. 81, no. 9, 1993, pp. 1215–1247.
3. H.J. McDermott, "Music Perception with Cochlear Implants: A Review," Trends in Amplification, vol. 8, no. 2, 2004, pp. 49–82.
4. J.-J. Sit et al., "A Low-Power Asynchronous Interleaved Sampling Algorithm for Cochlear Implants that Encodes Envelope and Phase Information," IEEE Trans. Biomedical Eng., vol. 54, no. 1, 2007, pp. 138–149.
5. Z.M. Smith, B. Delgutte, and A.J. Oxenham, "Chimaeric Sounds Reveal Dichotomies in Auditory Perception," Nature,7 Mar. 2002, pp. 87–90.
6. L.M. Friesen et al., "Speech Recognition in Noise as a Function of the Number of Spectral Channels: Comparison of Acoustic Hearing and Cochlear Implants," J. Acoustical Soc. of America, vol. 110, no. 2, 2001, pp. 1150–1163.
7. V. Looi et al., "Comparisons of Quality Ratings for Music by Cochlear Implant and Hearing Aid Users," Ear and Hearing, vol. 28, no. 2, 2007, pp. 59S–61S.
8. K. Nie, G. Stickney, and F.-G. Zeng, "Encoding Frequency Modulation to Improve Cochlear Implant Performance in Noise," IEEE Trans. Biomedical Eng., vol. 52, no. 1, 2005, pp. 64–73.
9. A.E. Vandali et al., "Pitch Ranking Ability of Cochlear Implant Recipients: A Comparison of Sound-Processing Strategies," J. Acoustical Soc. of America, vol. 117, no. 5, 2005, pp. 3126–3138.
10. R. Sarpeshkar et al., "An Analog Bionic Ear Processor with Zero-Crossing Detection," Proc. IEEE Int'l Solid-State Circuits Conf. (ISSCC05), IEEE Press, 2005, pp. 78–79.
11. R. Sarpeshkar et al., "An Ultra-Low-Power Programmable Analog Bionic Ear Processor," IEEE Trans. Biomedical Eng., vol. 52, no. 4, 2005, pp. 711–727.
12. R. Sarpeshkar, "Analog Versus Digital: Extrapolating from Electronics to Neurobiology," Neural Computation, vol. 10, no. 7, 1998, pp. 1601–1638.
13. B.S. Wilson et al., "Better Speech Recognition with Cochlear Implants," Nature,18 July 1991, pp. 236–238.
14. G. Cauwenberghs and V.A. Pedroni, "A Charge-Based CMOS Parallel Analog Vector Quantizer," Proc. Advances in Neural Information Processing Systems 7 (NIPS 94), MIT Press, 1994, pp. 779–786.
15. G.E. Loeb, "Are Cochlear Implant Patients Suffering from Perceptual Dissonance?" Ear and Hearing, vol. 26, no. 5, 2005, pp. 435–450.

Index Terms:
cochlear implant, fine-timing information, asynchronous, electrode stimulation, analog processor, phase information, music processor, neural stimulation, low power
Ji-Jon Sit, Rahul Sarpeshkar, "A Cochlear-Implant Processor for Encoding Music and Lowering Stimulation Power," IEEE Pervasive Computing, vol. 7, no. 1, pp. 40-48, Jan.-March 2008, doi:10.1109/MPRV.2008.3
Usage of this product signifies your acceptance of the Terms of Use.