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Asymmetric hair bundle Motion in chick cochlear hair cells
Otolaryngology Head and Neck Surgery P90
Research Forum --Monday
August 1997
the nonsyndromic hereditary hearing impairment consortium supported by the Ministry of Health and Welfare of Japan. The goals and objectives of the consortium are to become a resource for nonsyndromic hereditary hearing impairment and to map the genes that cause hearing impairment. Membership is open. The consortium anonymously collects demographic, genetic, audiologic, and medical information from hearing-impaired individuals through electronic and questionnaire survey. Blood samples are collected from the affected individuals. The consortium can extract DNA from blood samples and store DNA with the investigator's permission. The structure and procedure of our consortium will be presented and discussed.
cells to a lesser degree than that of ipsilateral axonal loss. Possible reasons for and implications of axonal loss will be discussed. (Supported in part by a 1995 AAO/HNSF Resident Research Grant and The Center for Neural Communication Technology funded by NIH/NCRR Grant P41-RRO9754-02.)
Poster 20
Action potentials were recorded from the round window of guinea pigs. Stimuli were 1 msec tone-bursts presented at 4, 8, 16, and 32 kHz frequencies. These tone-bursts were presented singly or in 24-stimulus trains. The 24-stimulus trains contained different frequencies and intensities, which were designed to avoid response adaptation by separating stimuli in frequency, intensity, and time. Response thresholds, as well as latency and amplitude functions, were recorded. Responses to single stimuli presented with an interstimulus interval of 190 msec were compared with those obtained by using trains of stimuli with intratrain intervals of 12, 7, and 3.5 msec. A comparison of responses obtained from individually presented stimuli with those from the 24stimulus trains showed no significant differences in response latency. Furthermore, the variability in response latency to the 24-stimulus trains was found to be statistically no different from the variability found in response latency to individually presented tone-bursts. As single tone bursts have already been shown to possess clinically acceptable reliability in response latency (Fausti et al. 1991), this study indicates that responses generated by 24-stimulus tone-burst trains should also be clinically reliable. The use of properly designed stimulus trains with short intrastimulus intervals can result in 92% time savings as compared with single stimulus presentation methods. This fast, reliable method of generating electrocochleographic responses is potentially useful for intensive care and intraoperative monitoring in humans, as well as in experimental situations in which recording time is limited. (This research was supported by Department of Education H235K30001 and NIH-NIDCD R01-DC01052.)
Feasibility of Chronic Auditory Nerve Implantation Using a Thin-Film Microelectrode Array DEREK A. JONES, MD (presenter), H. ALEXANDER ARTS, MD, JAMILLE F. HETKE, MS, and DAVID J. ANDERSON, PhD, Ann Arbor, Mich.
Direct implantation of the cochlear nerve with a penetrating microelectrode for prosthetic stimulation of the auditory system has several theoretical advantages over scala tympani stimulation including reduced power requirements, improved selectivity of stimulation, and applicability in dysmorphic cochleae. Previous acute electrophysiologic studies in our laboratory have demonstrated the feasibility of direct auditory nerve stimulation in cats with a thin-film microelectrode developed at the University of Michigan. A series of experiments was performed to further assess the feasibility of direct auditory nerve implantation by evaluating organism and tissue tolerance in a chronic cat model. Seven chronic experiments were performed in which a thin-film microelectrode array was implanted in the distal cochlear nerve via a transmastoid, transcochlear approach to the internal auditory canal under sterile conditions in anesthetized cats. After 2 months, the animals were euthanized, and the temporal bones were harvested for histologic evaluation. The auditory nerves were postfixed in osmium tetroxide, embedded in an epoxy resin, and sectioned in an axial plane to evaluate axonal loss. The temporal bones were decalcified and processed by using standard techniques. Midmodiolar sections were obtained to assess the cochlea and spiral ganglion. Six of the seven animals survived until sacrifice. One animal died during surgery due to anesthetic complications. One animal developed a fluid collection, presumably CSF, which resolved with conservative management. All of the animals developed a vestibular deficit for which they compensated within a few days. None of the animals developed meningitis or other neurologic sequelae. Histologic analysis confirmed placement of the electrode in the cochlear nerve. The auditory nerve on the implanted side uniformly demonstrated significant loss of axons. Cochlear histology on the operated side revealed fibrous tissue in the scala tympani, endolymphatic hydrops, and loss of spiral ganglion
Poster 21
Reliability of Rapidly Acquired Cochlear Action Potential Responses With Multiple Frequency and Intensity Tone Bursts in 24-Stimulus Trains B. ROBERTGIBSON, BA (presenter), CURTIN R. MITCHELL PhD, and SYDNEYGUITJENS, BA, Portland, Ore.
Poster 22
Asymmetric Hair Bundle Motion in Chick Cochlear Hair Cells MARC D. EISEN, BA (presenter), R. KEITHDUNCAN, MS, and JAMES C. SAUNDERS, PhD, Philadelphia and Drexel Hill, Pa.
Relative stereocilia motion has been studied in the sensory hair bundles of a number of species, but the symmetry of this motion has not been characterized. In this study we measured the symmetry of motion of the shortest hair in the bundle with respect to its resting state.
Research Forum --Monday
August 1997
the nonsyndromic hereditary hearing impairment consortium supported by the Ministry of Health and Welfare of Japan. The goals and objectives of the consortium are to become a resource for nonsyndromic hereditary hearing impairment and to map the genes that cause hearing impairment. Membership is open. The consortium anonymously collects demographic, genetic, audiologic, and medical information from hearing-impaired individuals through electronic and questionnaire survey. Blood samples are collected from the affected individuals. The consortium can extract DNA from blood samples and store DNA with the investigator's permission. The structure and procedure of our consortium will be presented and discussed.
cells to a lesser degree than that of ipsilateral axonal loss. Possible reasons for and implications of axonal loss will be discussed. (Supported in part by a 1995 AAO/HNSF Resident Research Grant and The Center for Neural Communication Technology funded by NIH/NCRR Grant P41-RRO9754-02.)
Poster 20
Action potentials were recorded from the round window of guinea pigs. Stimuli were 1 msec tone-bursts presented at 4, 8, 16, and 32 kHz frequencies. These tone-bursts were presented singly or in 24-stimulus trains. The 24-stimulus trains contained different frequencies and intensities, which were designed to avoid response adaptation by separating stimuli in frequency, intensity, and time. Response thresholds, as well as latency and amplitude functions, were recorded. Responses to single stimuli presented with an interstimulus interval of 190 msec were compared with those obtained by using trains of stimuli with intratrain intervals of 12, 7, and 3.5 msec. A comparison of responses obtained from individually presented stimuli with those from the 24stimulus trains showed no significant differences in response latency. Furthermore, the variability in response latency to the 24-stimulus trains was found to be statistically no different from the variability found in response latency to individually presented tone-bursts. As single tone bursts have already been shown to possess clinically acceptable reliability in response latency (Fausti et al. 1991), this study indicates that responses generated by 24-stimulus tone-burst trains should also be clinically reliable. The use of properly designed stimulus trains with short intrastimulus intervals can result in 92% time savings as compared with single stimulus presentation methods. This fast, reliable method of generating electrocochleographic responses is potentially useful for intensive care and intraoperative monitoring in humans, as well as in experimental situations in which recording time is limited. (This research was supported by Department of Education H235K30001 and NIH-NIDCD R01-DC01052.)
Feasibility of Chronic Auditory Nerve Implantation Using a Thin-Film Microelectrode Array DEREK A. JONES, MD (presenter), H. ALEXANDER ARTS, MD, JAMILLE F. HETKE, MS, and DAVID J. ANDERSON, PhD, Ann Arbor, Mich.
Direct implantation of the cochlear nerve with a penetrating microelectrode for prosthetic stimulation of the auditory system has several theoretical advantages over scala tympani stimulation including reduced power requirements, improved selectivity of stimulation, and applicability in dysmorphic cochleae. Previous acute electrophysiologic studies in our laboratory have demonstrated the feasibility of direct auditory nerve stimulation in cats with a thin-film microelectrode developed at the University of Michigan. A series of experiments was performed to further assess the feasibility of direct auditory nerve implantation by evaluating organism and tissue tolerance in a chronic cat model. Seven chronic experiments were performed in which a thin-film microelectrode array was implanted in the distal cochlear nerve via a transmastoid, transcochlear approach to the internal auditory canal under sterile conditions in anesthetized cats. After 2 months, the animals were euthanized, and the temporal bones were harvested for histologic evaluation. The auditory nerves were postfixed in osmium tetroxide, embedded in an epoxy resin, and sectioned in an axial plane to evaluate axonal loss. The temporal bones were decalcified and processed by using standard techniques. Midmodiolar sections were obtained to assess the cochlea and spiral ganglion. Six of the seven animals survived until sacrifice. One animal died during surgery due to anesthetic complications. One animal developed a fluid collection, presumably CSF, which resolved with conservative management. All of the animals developed a vestibular deficit for which they compensated within a few days. None of the animals developed meningitis or other neurologic sequelae. Histologic analysis confirmed placement of the electrode in the cochlear nerve. The auditory nerve on the implanted side uniformly demonstrated significant loss of axons. Cochlear histology on the operated side revealed fibrous tissue in the scala tympani, endolymphatic hydrops, and loss of spiral ganglion
Poster 21
Reliability of Rapidly Acquired Cochlear Action Potential Responses With Multiple Frequency and Intensity Tone Bursts in 24-Stimulus Trains B. ROBERTGIBSON, BA (presenter), CURTIN R. MITCHELL PhD, and SYDNEYGUITJENS, BA, Portland, Ore.
Poster 22
Asymmetric Hair Bundle Motion in Chick Cochlear Hair Cells MARC D. EISEN, BA (presenter), R. KEITHDUNCAN, MS, and JAMES C. SAUNDERS, PhD, Philadelphia and Drexel Hill, Pa.
Relative stereocilia motion has been studied in the sensory hair bundles of a number of species, but the symmetry of this motion has not been characterized. In this study we measured the symmetry of motion of the shortest hair in the bundle with respect to its resting state.