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> Cochlear Implants > Evoked Potentials
The Cochlear Implant Laboratory is funded by two large grants from The National Institutes of Health (NIH) and by smaller grants from manufacturers of cochlear implants. Our research group, at present, consists of Professor Michael F. Dorman, Tony Spahr, Ph.D., and Kathy Wexler, M.S. Louise Loiselle, M.S. is a doctoral student. Callen Shutters is our patient travel coordinator.
Cochlear Implants: Our experience with cochlear implants dates to the early 1980’s when Professor Dorman joined Luther Smith at Symbion, Inc. to explore the performance of the first multichannel cochlear-implant manufactured in the United States – the 4-channel, Ineraid cochlear implant. That project evolved and moved, first, to the University of Utah School of Medicine and then to Arizona State University. Currently, our main research efforts are (i) to investigate combined acoustic and electric stimulation (EAS) for patients with residual low-frequency hearing and (ii) to evaluate the benefits of current steering for improving the perception of speech and music by conventional cochlear implant patients. EAS is for patients who have residual hearing (thresholds of 60 dB or better) at 500 Hz but who have little or no residual hearing at 1000 Hz (70 dB or worse). An electrode is inserted partially into the cochlea (from 10 to 20 mm) with the aim of (i) preserving the low-frequency acoustic hearing and (ii) stimulating higher frequencies electrically. Both longer and shorter electrodes have been successfully inserted into cochlea with preservation of low frequency auditory thresholds. Our research looks into how well these patients perform relative to conventional implant patients and into when and how acoustic and electric hearing combine in the perception of speech, voice and music. Current steering is a signal processing technique which allows current to be directed to locations between physical electrodes. This is accomplished by delivering simultaneous pulses to two electrodes at once. By varying the magnitude of the pulses delivered to the two electrodes, current can be steered to multiple locations. We have found that most patients can hear several pitch percepts between electrode contacts. Thus, current steering allows the addressing of a large number of places along the cochlear partition. Our current research aims to harness current steering to increase the number of functional channels of stimulation delivered by a cochlear implant.
Evoked Potentials -- Neural Plasticity: In this work – a joint project with Anu Sharma, Ph.D. and her large research group at The Auditory Cortical Function Laboratory, University of Texas at Dallas/Callier Center for Communication Disorders -- we use the morphology and latency of cortical auditory-evoked potentials (the P1 response) to assess the development, deterioration and plasticity of central auditory pathways in normal-hearing children, children with hearing-impairments and profoundly deaf children fit with cochlear implants. We have found a critical period for stimulation of central auditory pathways. If stimulation begins within a time window of about 3.5 years following birth, then the pathway can develop in a normal fashion. However, if stimulation is delayed by more than 7 years, then the pathway will not develop normally when stimulation is begun. Our estimates of a critical period are broadly consistent with estimates of ages below which speech and language skills can develop normally in children fit with a cochlear implant. We are currently working to (i) create new age norms for the development of central auditory pathways, (ii) to assess the effects of mild, moderate and severe hearing impairment on the maturation of the central auditory pathway, (iii) to assess the effects of the age of bilateral cochlear implantation on the development of the auditory pathway and (iv) to assess ‘take-over’ by vision or other sensory modalities of un-stimulated areas of auditory cortex. The Cochlear Implant Laboratory at the University of Texas at Dallas (UTD) The Auditory Cortical Function Laboratory at UTD The Callier Center for Communication Disorders, UTD
If you would like to volunteer to participate in one (or more) of our research projects, please visit the "Participate in Research" page, complete the on-line interest form, and submit it. If you prefer other methods of contact, please visit our contact page or indicate it in your message.
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