W. M. Rabinowitz
D. K. Eddington
J. Tierney
L. A. Delhorne
Res. Lab. of Electron., MIT, 50 Vassar St., Rm. 36-789, Cambridge, MA 02139
Each channel of a continuous-interleaved-stimulation (CIS) sound processor uses the compressed envelope of its bandpass-filtered output to modulate biphasic current pulses that are delivered to an intracochlear electrode. Pulses are interleaved across channels to avoid simultaneous field interactions, and pulse rates are high (~2000 pps/channel) to preserve temporal waveform cues. Using up to six monopolar electrodes directly accessible with the Ineraid implant, this strategy has shown considerable promise in acute evaluations conducted in the laboratory [Wilson et al., Nature 352, 236--238 (1991)]. In collaboration with a group in Innsbruck, a prototype portable real-time system has been developed (based on a DSP56001) that can realize some CIS implementations. Two subjects with 9 years of experience using the Ineraid analog sound processor are now wearing the CIS system on a full-time basis. After several weeks, one subject prefers the CIS strategy; however, objective measures of speech reception show no gains (re: the Ineraid processor). The second subject shows large gains with CIS and some evidence of continuing improvements. Without lipreading, he scores near perfect on relatively difficult (IEEE/Harvard) sentences in quiet; for speech reception in noise, he shows a deficit of 7 dB re: normal-hearing listeners. [Work supported by NIH.]