Project 2: Peripheral Electrophysiology

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Program Director/Principal Investigator (Last, First, Middle): Gantz, Bruce J. ABSTRACT – PROJECT 2 Cochlear implant (CI) technology is continually evolving. Today, CIs have been designed specifically to preserve cochlear structures and many recipients enjoy preservation of acoustic hearing in their implanted ear following surgery. Speech processors are also available that allow coordinated delivery of sound via both acoustic and electric stimulation modes. We refer to this group of CI users as A+E listeners and they are the focus of this proposal. Two specific aims will be addressed. Aim 1 starts with the observation that average performance levels for this group of CI users are good, but notes that there is still considerable variance in outcome for individuals. The studies included in this proposal are designed to identify reasons for that variance in outcome. We hypothesize that the status of the peripheral auditory system may be particularly important in determining outcome for A+E listeners. A series of electrophysiologic measures are proposed that we will use to characterize the response of the auditory periphery to both acoustic and electrical stimulation. The methods we propose to use are novel. In our previous work we have used electrical stimulation to assess the status of the auditory periphery. Electrical stimulation bypasses the cochlear hair cells. The studies included in this proposal will use acoustic stimulation and an electrode located inside the cochlea to record neural activity from both cochlear hair cells and from the auditory nerve. These responses to acoustic stimulation will complement measures of how the auditory nerve responds to electrical stimulation and the result will be a more comprehensive characterization of the integrity and function of the peripheral auditory system. We also propose, for the first time, to incorporate results of genetic testing into the model will use for predicting outcome. One series of experiments will focus on how spectral and temporal cues are processed at the auditory periphery and those results serve as independent variables in a multivariate regression analysis that will be used to determine the independent contributions of multiple factors to speech perception in noise. Our second aim will focus on using our expanded battery of electrophysiologic recording methods to help us understand the reason that a subset of A+E listeners experience loss of their acoustic hearing often months after surgery. We will follow each study participant closely and correlate changes in behavioral thresholds with changes in electrode impedance, current flow patterns within the cochlea and electrophysiologic measures of the response of the peripheral auditory system to both acoustic and electric stimulation. Our hypothesis is that changes over time in these metrics will inform theories regarding why this delayed loss of acoustic hearing takes place and, in turn, suggest potential treatment options. OMB No. 0925-0001/0002 (Rev. 03/16 Approved Through 10/31/2018) Page Continuation Format Page