Four cochlear implant users, having normal hearing in the unimplanted ear, compared the pitches of electrical and acoustic stimuli presented to the two ears. Comparisons were between 1,031-pps... Show moreFour cochlear implant users, having normal hearing in the unimplanted ear, compared the pitches of electrical and acoustic stimuli presented to the two ears. Comparisons were between 1,031-pps pulse trains and pure tones or between 12 and 25-pps electric pulse trains and bandpass-filtered acoustic pulse trains of the same rate. Three methods-pitch adjustment, constant stimuli, and interleaved adaptive procedures-were used. For all methods, we showed that the results can be strongly influenced by non-sensory biases arising from the range of acoustic stimuli presented, and proposed a series of checks that should be made to alert the experimenter to those biases. We then showed that the results of comparisons that survived these checks do not deviate consistently from the predictions of a widely-used cochlear frequency-to-place formula or of a computational cochlear model. We also demonstrate that substantial range effects occur with other widely used experimental methods, even for normal-hearing listeners. Show less
Setting: Cochlear implant (CI)/tertiary referral center. Subjects: Twenty-five patients implanted with an Advanced Bionics HiRes90K HiFocus1J CI. Study Design/Main Outcome Measures: A 3-dimensional... Show moreSetting: Cochlear implant (CI)/tertiary referral center. Subjects: Twenty-five patients implanted with an Advanced Bionics HiRes90K HiFocus1J CI. Study Design/Main Outcome Measures: A 3-dimensional cylindrical coordinate system is introduced using the basal turn of the cochlea as the x and y planes and the center of the modiolus as the z axis. The 0-degree angle is defined by the most lateral point of the horizontal semicircular canal. It is applied to both preoperative and postoperative computed tomographies in 25 patients. The angular position of the round window is examined. Interobserver reproducibility is tested by localization of all electrode contacts within the coordinate system. To observe realignment over time, electrode coordinates in postoperative images were projected on preoperative images. Additionally, comparison to existing imaging-related coordinate systems was made. Results: The angular position of the center of the round window is 34.6 +/- 0.4 degrees (standard deviation) with an intraclass coefficient of 1.00. The intraclass coefficient for interobserver reproducibility of the 16 electrode contacts ranged from 0.74 to 1 for the rotational angle (phi) and 0.77 to 1 for the distance to the modiolus (rho). In 21 of 25 patients, a perfect match or minimal displacement of up to 3 electrode contacts was seen. Comparison to existing systems showed good correlation. Conclusion: A 3-dimensional cochlear coordinate system easily applicable in clinical patients is described, which fulfills the requirements set by an international consensus. Show less
Hypothesis: An objective cochlear framework, for evaluation of the cochlear anatomy and description of the position of an implanted cochlear implant electrode, would allow the direct comparison of... Show moreHypothesis: An objective cochlear framework, for evaluation of the cochlear anatomy and description of the position of an implanted cochlear implant electrode, would allow the direct comparison of measures performed within the various subdisciplines involved in cochlear implant research. Background: Research on the human cochlear anatomy in relation to tonotopy and cochlear implantation is conducted by specialists from numerous disciplines such as histologists, surgeons, physicists, engineers, audiologists, and radiologists. To allow accurate comparisons between and combinations of previous and forthcoming scientific and clinical studies, cochlear structures and electrode positions must be specified in a consistent manner. Methods: Researchers with backgrounds in the various fields of inner ear research as well as representatives of the different manufacturers of cochlear implants (Advanced Bionics Corp., Med-El, Cochlear Corp.) were involved in consensus meetings held in Dallas, March 2005, and Asilomar, August 2005. Existing coordinate systems were evaluated, and requisites for an objective cochlear framework were discussed. Results: The consensus panel agreed upon a 3-dimensional, cylindrical coordinate system of the cochlea using the "Cochlear View" as a basis and choosing a z axis through the modiolus. The zero reference angle was chosen at the center of the round window, which has a close relationship to the basal end of the Organ of Corti. Conclusion: Consensus was reached on an objective cochlear framework, allowing the outcomes of studies from different fields of research to be compared directly. Show less
HYPOTHESIS:: An objective cochlear framework, for evaluation of the cochlear anatomy and description of the position of an implanted cochlear implant electrode, would allow the direct comparison of... Show moreHYPOTHESIS:: An objective cochlear framework, for evaluation of the cochlear anatomy and description of the position of an implanted cochlear implant electrode, would allow the direct comparison of measures performed within the various subdisciplines involved in cochlear implant research. BACKGROUND:: Research on the human cochlear anatomy in relation to tonotopy and cochlear implantation is conducted by specialists from numerous disciplines such as histologists, surgeons, physicists, engineers, audiologists, and radiologists. To allow accurate comparisons between and combinations of previous and forthcoming scientific and clinical studies, cochlear structures and electrode positions must be specified in a consistent manner. METHODS:: Researchers with backgrounds in the various fields of inner ear research as well as representatives of the different manufacturers of cochlear implants (Advanced Bionics Corp., Med-El, Cochlear Corp.) were involved in consensus meetings held in Dallas, March 2005, and Asilomar, August 2005. Existing coordinate systems were evaluated, and requisites for an objective cochlear framework were discussed. RESULTS:: The consensus panel agreed upon a 3-dimensional, cylindrical coordinate system of the cochlea using the "Cochlear View" as a basis and choosing a z axis through the modiolus. The zero reference angle was chosen at the center of the round window, which has a close relationship to the basal end of the Organ of Corti. CONCLUSION:: Consensus was reached on an objective cochlear framework, allowing the outcomes of studies from different fields of research to be compared directly. Show less
Cochlear implants (CI) are by now an accepted form of rehabilitation for profoundly deaf patients. CI users regain part of their hearing by direct electrical stimulation of the auditory nerve. With... Show moreCochlear implants (CI) are by now an accepted form of rehabilitation for profoundly deaf patients. CI users regain part of their hearing by direct electrical stimulation of the auditory nerve. With modern cochlear implants most users are able to achieve open-set speech understanding and are able to use the telephone. There are, however, still a lot of unanswered questions regarding the optimal design, stimulation paradigms, fitting methods and objective measurements. With the development of a realistic computer model of the implanted cochlea, as described in this thesis, these questions are analyzed from a fundamental perspective. This realistic model enables the analysis of clinical devices and gives insight in discrepancies between human and animal results. Insights gained from the model are used to improve clinical practice. Based on the model outcomes presented the characteristics of an improved electrode design were defined, and finally tested in a temporal bone study. Show less
