No abstract

Integration of cues from multiple sensory channels improves our ability to sense and respond to stimuli. Cues arising from a single event may arrive at the brain asynchronously, requiring them to be "bound" in time. The perceptual asynchrony between vestibular and auditory stimuli has been reported to be several times greater than other stimulus pairs. However, these data were collected using electrically evoked vestibular stimuli, which may not provide similar results to those obtained using actual head rotations. Here, we tested whether auditory stimuli and vestibular stimuli consisting of physiologically relevant mechanical rotations are perceived with asynchronies consistent with other sensory systems. We rotated 14 normal subjects about the earth-vertical axis over a raised-cosine trajectory (0.5 Hz, peak velocity 10 deg/s) while isolated from external noise and light. This trajectory minimized any input from extravestibular sources such as proprioception. An 800-Hz, 10-ms auditory tone was presented at stimulus onset asynchronies ranging from 200 ms before to 700 ms after the onset of motion. After each trial, subjects reported whether the stimuli were "simultaneous" or "not simultaneous." The experiment was repeated, with subjects reporting whether the tone or rotation came first. After correction for the time the rotational stimulus took to reach vestibular perceptual threshold, asynchronies spanned from -41 ms (auditory stimulus leading vestibular) to 91 ms (vestibular stimulus leading auditory). These values are significantly lower than those previously reported for stimulus pairs involving electrically evoked vestibular stimuli and are more consistent with timing relationships between pairs of non-vestibular stimuli.

current cochlear implants (cis) are semi-implantable devices with an externally worn sound processor that hosts the microphone and sound processor. A fully implantable device, however, would ultimately be desirable as it would be of great benefit to recipients. While some prototypes have been designed and used in a few select cases, one main stumbling block is the sound input. Specifically, subdermal implantable microphone technology has been poised with physiologic issues such as sound distortion and signal attenuation under the skin. Here we propose an alternative method that utilizes a physiologic response composed of an electrical field generated by the sensory cells of the inner ear to serve as a sound source microphone for fully implantable hearing technology such as cis. Electrophysiological results obtained from 14 participants (adult and pediatric) document the feasibility of capturing speech properties within the electrocochleography (ecochG) response. Degradation of formant properties of the stimuli /da/ and /ba/ are evaluated across various degrees of hearing loss. preliminary results suggest proof-of-concept of using the ecochG response as a microphone is feasible to capture vital properties of speech. However, further signal processing refinement is needed in addition to utilization of an intracochlear recording location to likely improve signal fidelity.To date, it is estimated that as many as 466 million individuals worldwide have hearing loss as defined as an average hearing level of ≥35 dB HL by pure-tone audiometry 1 . Treatment options for hearing loss typically depend on the severity of the hearing loss. Cochlear implants (CI) have long been a treatment option for individuals with severe-to-profound hearing loss; however, with advancements in technology, candidacy criteria have expanded to include individuals with greater amounts of residual hearing. With this trend, the focus has shifted toward developing techniques and technology to allow for the preservation of residual hearing, as this has been shown to be important in obtaining optimal outcomes through the use of electric-acoustic stimulation. That is, in patients who receive CIs but maintain some useable residual hearing, the implanted ear can be stimulated using the ipsilateral combination of electric (CI) and acoustic (hearing aid) 2,3 .In attempts to achieve preservation of residual hearing, implementation of electrocochleography (ECochG) at the time of CI surgery has recently been described. ECochG is a tool that allows electrophysiological assessment of the peripheral auditory system (i.e., the cochlea and auditory nerve) by using acoustic stimulation. Specifically, ECochG has been used as a monitoring tool during CI surgery in an effort to provide real-time feedback of inner ear physiology that allows for modifying surgical technique in an attempt to avoid trauma caused by the electrode insertion, hence preserving residual hearing 4-6 . The use of ECochG is not new, but its use in CI surgery is novel. Specifically, new technology ...

Objective: Given the heterogeneity of papers about electrocochleography (ECochG) and cochlear implantation (CI) and the absence of a systematic review in the current literature, the aim of this work was to analyze the uses of ECochG in the different stages of CI. Data Sources: A search of PubMed from inception to December 8, 2019, with cross-references, was executed. Keywords were: “Cochlear Implant” OR “Cochlear Implantation” AND “Electrocochleography” OR “ECochG.” The main eligibility criteria were English-language articles, investigating the use of ECochG in the different phases of CI. Study Selection: Literature reviews, editorials, case reports, conference papers were excluded, as were papers in which ECochG was just sporadically executed. Data Extraction: The quality of the included studies was assessed using “The Strengthening the Reporting of Observational Studies in Epidemiology” (STROBE) Statement. Data Synthesis: A total of 95 articles were identified and 60 papers were included. The included articles covered a timeframe from 2003 to 2019. Of the 60 papers, 46 were human studies, 12 animal studies, and two involved more data sets. Eleven related to the diagnostic phase, 43 described intraoperative monitoring, and 10 were regarding follow-up testing. Hearing preservation was the most discussed topic with 25 included articles. Conclusions and Relevance: ECochG measurements appeared to be useful in many aspects of CI, such as hearing preservation. Our review is the first that shows the evolution of the technique and how much has been achieved from the earliest experiments to the most recent signal process refinements and device implementation in CI.

Objective: Tip fold-over is a rare but serious complication of cochlear implant (CI) surgery. The purpose of this study was to present intraoperative electrocochleography (ECochG) observations in a series of CI electrode tip fold-overs. Patients: Five pediatric subjects undergoing CI surgery through a round window (RW) approach with a perimodiolar electrode array, who were diagnosed with either auditory neuropathy spectrum disorder or enlarged vestibular aqueduct. Interventions: Intraoperative RW ECochG during CI surgery: tone burst stimuli were presented from 95 to 110 dB SPL. Main Outcome Measure(s): Magnitude and phase characteristics of ECochG responses obtained intraoperatively before and immediately after electrode insertion were examined for patients with and without tip fold-over. Results: Three subjects presented with tip fold-over and two formed the control group. Among fold-over cases, one participant exhibited an inversion in the starting phase of the cochlear microphonic response and a decrease in spectral magnitude from pre- to postinsertion. Both subjects who did not exhibit a change in phase had an increase in the ECochG-total response (ECochG-TR) magnitude. No case in the control group exhibited a change in starting phase. In regard to the ECochG-TR, all controls showed a decrease in the magnitude. Conclusions: Despite the small number of patients, heterogeneous ECochG response patterns were observed within the fold-over group. Though these results are not conclusive, they can serve as a framework to begin to understand ECochG's utility in detecting intraoperative tip fold-over.