Amélie Guex

Amélie Guex

Faculty Mentor: Daniel J. Lee, M.D., F.A.C.S.
Massachusetts Eye and Ear Infirmary Department of Otology and Laryngology
Amélie  Guex

Project Summary: The focus of this project is to study the use of pulsed laser light to stimulate the central auditory system. This novel approach may be a means to improve the efficacy of the current generation of electrically based Auditory Brainstem Implants (ABI).
These devices are used in patients who have a disconnection between the peripheral and central auditory systems. This cohort usually suffers with Neurofibromatosis Type 2, an autosomal dominant condition that characteristically causes benign tumors to grow on the hearing nerves on both sides. Removal of the tumors or the tumors themselves often destroy the nerves, meaning other hearing devices such as hearing aids or cochlear implants are unable to work. The ABI bypasses the cochlea and auditory nerve to directly stimulate the cochlear nucleus, the point where the hearing nerve usually enters the brainstem. Current ABI devices use electric current and patient results seem to be limited by the spread of this current, leading to non-auditory side effects and smeared hearing perception. Optically-based methods appear to stimulate neurons more selectively and may overcome some of the problems associated with non-focused stimulation.
One part of this study will be the comparison of optical and electrical activation of the cochlear nucleus (CN) on a rodent model. Optically evoked auditory brainstem responses will be characterized. We will then explore the response and spatial extent of stimulation by recording Inferior Colliculus (IC) responses of the electrical and optical stimulation to determine if higher spatial selectivity can be seen during infrared neural stimulation (INS).
We will also explore the use of blue light laser stimulation of the auditory system. Neurons can be activated by blue light if the subject expresses a light-sensitive ion channel protein, Channelrhodopsin-2. Patterns of responses to optical stimulation will be analysed and compared to INS in both transgenic and wild type mice.
My role in the project will be to analyze the data obtained from the ABR and IC recordings. Using MATLAB based programming I will characterize the responses and frequency specificity to optimize the stimulation parameters.This work will further our understanding of the central auditory system and help to identify optimal areas for placement of auditory neuroprostheses for maximal patient benefit.

Published Articles:

Conducting polymer electrodes for auditory brainstem implants. Journal of Materials Chemistry B. Issue 25. 2015. Link to article

Auditory responses to electric and infrared neural stimulation of the rat cochlear nucleus. Hearing Research. Vol 310. April 2014. Pages 69–75. Link to article


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