The current standard of care for cochlear implants (CI) does not address the significant pitch-place mismatch that is inherent in cochlear implantation (see detailed description below). The present study uses postoperative Flat Panel (higher resolution than standard) CT imaging to measure where CI electrodes sit within an individual's cochlea; doing so allows for more accurate frequency mapping (and thus pitch perception). The hypothesis of this study is that long-term (1 year) use of CT image-based frequency maps, beginning on the first day of CI activation, will improve user performance in the areas of speech and music perception, as compared to the use of default programming settings.

Pitch perception is a fundamental component of how humans process sound. Individuals who use cochlear implants (CIs), surgically implanted devices which are able to restore a limited range of hearing, struggle with pitch perception for a variety of reasons. Although CIs can often restore the ability to hear speech from a single talker in quiet, perception of more complex auditory stimuli like music is severely limited. CI users often report music as being difficult, even displeasing, to listen to. These experiences can be immensely frustrating, especially for people who experience deafness later in life and have built strong emotional attachments to music, such as musicians or audiophiles.

Cochlear implant programming (also called "mapping") is done using a set of generally-accepted default settings without taking into account individual differences of precisely where CI electrodes are physically located in the cochlea. For this reason, CI users commonly experience a place-pitch mismatch between the stimulation by an electrode in response to a given frequency and the actual frequency specified by the original cochlear location. CI users vary widely in their ability to adapt to place-pitch mismatch; some adapt completely, others partially, and others not at all. The length of time in which an individual takes to adapt is also highly variable. Bilateral CI users may have differing adaptation between ears, leading to distortion of sound localization and speech in noise perception abilities.

Flat Panel Computed Tomography (FPCT) is an imaging technique that consistently produces high quality images with identification of the delicate cochlear structures and the cochlear implant (CI) electrode contacts. FPCT imaging of the cochlea, combined with 3D curved multiplanar reconstruction (MPR) software, has been shown to yield reliable cochlear duct length measurements. With these resources, measurements of cochlear length and determination of intracochlear electrode location relative to standardized cochlear landmarks can be produced. These data are then utilized to create individualized frequency allocation tables relevant to the actual physical location of CI electrode contacts.

In this study, FPCT imaging, 3D curved MPR, and applied mathematics are used to quantify the difference between theoretical and actual electrode contact placement with respect to pitch-place mapping. Previous results have revealed significant deviations between predicted and programmed characteristic frequencies, which are relevant for accurate speech, pitch, and music perception. The goal of the study is to gather FPCT scans on a cohort of 20 new CI recipients, and characterize the impact of long-term (1 year) personalized pitch-place maps on a battery of speech and music metrics. The performance with the FPCT-based programs will then be compared to performance using the manufacturer default settings.

The novel aspect of this study involves working with newly implanted CI recipients and programming these patients with custom CT-based programs. More specifically, CT-based programs will be given to new CI recipients before any acclimation or programming of clinical default maps occur. This differentiates the study from prior ones, as CT-based programming has only been investigated in populations who have already used clinical default maps for some substantial period of time (e.g. for 3 months, 5 years, etc.). Participants will participate in a series of testing sessions to evaluate their speech and music perception abilities over the course of the study. At the end of the study, participants will be allowed to keep their preferred listening programs (i.e., experimental and/or default program).

The researcher team hypothesizes that bypassing the use of a clinical-based map is imperative to fully understanding the effects of CT-based programming, as those who have already used clinical default programs demonstrate much higher degrees of place-pitch mismatch at baseline. By providing a new CI recipient with a custom CT-based program on their very first day of electrical hearing (CI activation), there is a unique and novel opportunity to minimize pitch-place mismatch from the outset, and to bypass the period of time that the vast majority of CI recipients have when first adapting to a clinical default program.

Inclusion Criteria:

• Has or plans to have a MED-EL cochlear implant (CI)
• Has not yet had their CI activated
• Be able and willing to participate in all of the research appointments for follow-up testing (e.g., 1, 3, 6, 12, and 13 months post-CI activation)
• Be willing to use the CI full-time (during waking hours) for 13 months post-activation
• Is able to speak and read American English
• Uses oral/aural communication as primary communication modality

Exclusion Criteria:

• Intra-cochlear electrodes known to be open or short-circuits
• Partially-inserted CI with fewer than 10 intra-cochlear electrodes
• Any concomitant condition(s) that may affect performance on speech and music test battery (e.g., cognitive impairment)
• Atypical cochlear anatomy (e.g., fewer than 2 turns of the cochlea)
• Pregnancy (a contraindication for CT scan)

Data/results from participants of this study will be de-identified prior to publication. Data and materials from this study will be uploaded to the repository provided by the Library of the University of California, San Francisco (Dryad).

Data and materials will become available after the corresponding manuscript has completed a peer review process and is accepted for publication.

Publicly available