Document Type : Full Research Paper


1 Electrical Engineering Department, AmirKabir University of Technology

2 Medical Science Department, Tarbiat Modarres University



Auditory nerve fibers stimulating using electrical current with implanted electrodes are the basis of cochlear implant system. Therefore, expansion of current spread in volume conductor will change the electrical potential in a larger region. This expansion causes larger region stimulation and decreases the accuracy and resolution of the stimulation in both the possibility of investigation of a particular region at Neural Response Telemetry (NRT) tests and also in hearing stimulation. Therefore, narrowing the width of stimulated region is the main goal in the selective stimulation. The conventional multi polar stimulation methods use lateral inhibitory electrode to form the spatial pattern of the electrical potential distribution for narrowing the stimulated region, but it needs to simultaneous stimulation of the electrodes, which is not available in implanted systems. In this paper, a new non-simultaneous multi-electrode stimulation method has been presented, which is based on applying the inhibitory pre-pulses by lateral electrodes. Inhibitory effect of the lateral electrodes pulses changes the initial conditions of the fibers and their thresholds. The results of simulations show that this method will solve the problem of simultaneous stimulation in conventional tri-polar stimulation methods and also is effective at controlling of stimulation area, comparing with tri-polar stimulation area, qualitatively and quantitatively.


[1]     Spelman FA; The past, present, and future of cochlear prostheses accomplishments and challenges in treating sensorineural deafness through electrical stimulation; IEEE Eng in Medicine & Biology 1999; 27-33.
[2]     Miyoshi S, Ifukube T, Matsushima J; Proposal of new method for narrowing and moving the stimulated region of cochlear implant; IEEE Trans on Biomedical Eng April 1999; 46(4):451-460.
[3]     Litvak L; Toward a better speech processor for cochlear implant: auditory nerve response to high rate electric pulse train; PhD Thesis, MIT 2002.
[4]     Brill SM, Gstottner W, Helms J, Ilberg CV, Baumgartner W, Muller J, Kiefer J; Optimization of channel number and stimulation rate for the fast continuous interleaved sampling strategy in the COMBI 40+; The American Journal of Otology 1997.
[5]     Zimerling MJ, Hochmair ES; EAP recording in ineraid patients-correlations with psychophysical measures and possible implications for patient fitting; Ear & Hearing April 2002; 23(2):81-91.
[6]     Huang CQ, Shepherd RK, Carter PM, Seligman PM, Tabor B; Electrical stimulation of the auditory nerve : direct current measurment in vivo; IEEE Trans on Biomedical Eng April 1999; 46(4):461-470.
[7]     Liang DH, Lusted HS, White RL; The nerve electrode interface of the cochlear implant: current spread; IEEE Trans on Biomedical Eng January 1999; 46(1):35-92.
[8]     Frijns JHM, Schoonhoven R, Grote JJ; The influence of stimulus intensity on spike timing and the compound action potential in the electrically stimulated cochlea: a model study; 18th Annual International Conference of the IEEE Eng in Medicine and Biology Society 1996; 327-328.
[9]     Shinogami M, Kaga K, Sugasawa T, Nakamura M, Takai S; Electrical stimulation test for residual hearing ears using electro audiometer; Japan Congress of Audiology October 1996.
[10] Jolly CN, Spelman FA, Clopton BM; Quadrupolar stimulation for cochlear prostheses: modeling and experimental data; IEEE Trans on Biomedical Eng August 1996; 43(8):857-865.
[11] Rubinstein JT, Miller A, Mino H, Abbas P; Analysis of monophasic and biphasic electrical stimulation of nerve; IEEE Trans on Biomedical Eng October 2001; 48(10):1065-1070.
[12] Frijis JHM, Mooij J, ten Kate JH; A Quantitative approach to modeling mammalian myelinated nerve fibers for electrical prosthesis design; IEEE Trans on Biomedical Eng June 1994; 41(6):526-566.
[13] McNeal D; Analysis of a model for excitation of myelinated nerve; IEEE Trans on Biomedical Eng December 1976; 23(4):329-337.
[14] Warman EN, Warren M, Daurand D; Modeling the effects of electric fields on nerve fibers: determination of excitation threshold; IEEE Trans on Biomedical Eng December 1992; 39(12):1244-1254.
[15] Rattay F; Analysis of model for extracellular fiber stimulation; IEEE Trans on Biomedical Eng December 1989; 36(7):676 682.
[16] Rubinstain JT; Axon termination conditions for electrical stimulation; IEEE Trans on Biomedical Eng July 1993; 40(7):654 663.
[17] Barr RC, Plonsey R; Threshold variability in fibers with field stimulation of excitable membranes; IEEE Trans on Biomedical Eng December 1995; 42(12):1185-1191.