Speech Understanding by Cochlear-Implant Patients with Different Left- and Right-Ear Electrode Arrays Michael F. Dorman and Lisa Dahlstrom Electrode-pitch rankings and monaural and binau- ral speech perception scores were obtained from two patients fit with a Med El CIS-Link processor and Ineraid electrode array in one ear and a Clarion processor and Hi-Focus electrode array in the other ear. The results of the electrode-ranking task indi- cated that current from the Hi-Focus electrodes extended more apically than current from the In- eraid array, i.e., the two most apical Hi-Focus elec- trodes were ranked lower in pitch than the most apical Ineraid electrode. Because of this and be- cause of the different number of active electrodes in the two arrays, it is likely that the two cochleae presented different representations of the same sig- nal to more central stages of information process- ing. In spite of this, both patients achieved better scores when both implants were activated than when the implants were activated one at a time. (Ear & Hearing 2004;25;191–194) Binaural cochlear implants are likely to provide better speech understanding than a monaural im- plant in two conditions: (i) when the electrodes in the two ears are inserted to the same depth and, as a consequence, the outputs of the two auditory peripheries are frequency matched, or (ii) when the electrodes in the two ears are inserted to different depths and the information from the two electrode arrays is complementary (Lawson, Wolford, Brill, Schatzer, & Wilson, Reference Note 1; Long, Edding- ton, Colburn, & Rabinowitz, 2003). From this point of view it is of interest to investigate the perfor- mance of binaural patients in whom the electrode arrays differ in terms of place of stimulation and number of electrodes. At issue is whether central processing for speech perception can accommodate mismatched signals from the auditory periphery and provide an advantage for two ears versus a single ear. To find out, monaural and binaural speech perception tests were carried out on two patients fit with a four- or five-electrode Ineraid array in one cochlea and an eight-electrode Clarion Hi-Focus array in the other. METHODS Subjects and Devices Patient U-1 acquired a severe hearing loss follow- ing meningitis at age 6. The loss progressed sud- denly to profound hearing loss in his left ear at age 10 and in his right ear by age 15. He was fit with the four-channel Ineraid processor and six-electrode ar- ray in his left ear at age 21. He received a Med El CIS-Link processor for his left ear at age 25. The processor was programmed to output to the five most apical electrodes because stimulation on elec- trode 6 was described as unpleasant. Pulse duration was 40 s/phase and pulse rate was 833 pulses/sec/ channel. At age 31, Patient U-1 was fitted with the Clarion implant and eight-electrode Hi-Focus array in his right ear. The Clarion device was programmed in continuous interleaved sampling (CIS) mode to output to all 8 electrodes. Pulse duration was 75 s/phase and pulse rate was 813 pulses/sec/channel. At the time of testing, Patient U-1 had used the two processors together for a period of approximately 3 wk. Patient U-2 had a progressive hearing loss of unknown origin. Her hearing loss was detected at age 9 and progressed to profound at age 33. Patient U-2 was fitted with the Ineraid device and electrodes in her right ear at age 55. Only electrodes 1, 2, 3, and 5 were functional. She received a Med El CIS-Link processor for the right ear at age 70. The processor was programmed to output to the four functional electrodes. Pulse duration was 40 s/phase and pulse rate was 3030 pulses/sec/channel. Patient U-2 was fit with the Clarion C1 device and Hi-Focus electrode array in her left ear at age 71. The Clarion device was programmed to output to all eight elec- trodes using a MPS strategy. Pulse duration was 70 s/phase and pulse rate was 1414 pulses/sec/chan- nel. At the time of testing, Patient U-2 had used the two processors for a period of approximately 1 mo. Filter-to-Electrode Mapping For the Clarion devices, the center frequencies of the bandpass filters for electrodes 1– 8 were 418 Hz, 604Hz, 861 Hz, 1213 Hz, 1703Hz, 2280 Hz, 3143 Hz, and 44572 Hz, respectively. For Patient U-1, the center frequencies of the CIS-Link bandpass filters Arizona State University, Tempe, Arizona (M.F.D.) and Univer- sity of Utah Health Sciences Center, Salt Lake City, Utah (M.F.D., L.D.) DOI: 10.1097/01.AUD.0000120367.70123.9A 0196/0202/04/2502-0191/0 • Ear & Hearing • Copyright © 2004 by Lippincott Williams & Wilkins • Printed in the U.S.A. 191