Much of the hospital's success in identifying and treating children with hearing loss is the result of the rapid transfer of research findings from laboratories to clinic and bedside.

Areas of Research - Clinical and Behavioral Studies of Human Communication - Cochlear Implant Research Laboratory

Overview

Research in the Cochlear Implant Laboratory is aimed at investigating the relationship between subjective and objective measures obtained with electrical stimulation of the human auditory system. Subjective (or behavioral) measures require active participation on the part of the research subject. Examples of subjective measures include listening to sounds and making judgments about certain aspects of the sound (e.g., loudness or pitch) or listening to speech presented in different conditions and repeating words or sentences. Objective measures do not require active participation from the subject. The objective measures made in our laboratory consist of measurements made from the auditory pathways in response to electrical stimulation from the subject’s cochlear implant. The goal of this research is to determine whether certain objective measures can be used to predict certain behavioral measures. We hope to use this information to find better ways to program cochlear implant speech processors for children and adults.

Facilities

The laboratory consists of three rooms: (1) a large sound-attenuating booth equipped with a sound field system, recliner, television, VCR/DVD player, impedance bridge, and touch-screen monitor; (2) an adjacent control room equipped with an audiometer, a networked color printer, two laptops, one PC, and cochlear implant speech processor interfaces for controlling psychophysical and physiologic experiments; (3) general lab space equipped with a pediatric table and chairs, toy chest, desk space and computer for a research assistant, file storage, and lab meeting space.

Staff

The laboratory is directed by Michelle L. Hughes, Ph.D., CCC-A. Research assistant is Lisa Stille, M.A., CCC-A. All staff members are certified audiologists.

Summary of Research Program

For Clinicians and Scientists

This research program focuses on better understanding the relation between electrophysiologic and psychophysical measures in cochlear implants. Present experiments are aimed at examining electrophysiologic and psychophysical measures of channel interaction with both simultaneous and non-simultaneous stimulation. Channel interaction can occur when multiple electrodes in a cochlear implant stimulate the same region within the cochlea. Channel interactions may have effects on speech perception with a cochlear implant, although the extent of this is not entirely clear. Psychophysical measures of channel interaction could be useful in determining optimal speech processor settings; however, these measures are time consuming and unfeasible with young children. In contrast, electrophysiologic channel interactions can be measured quickly with the electrically evoked compound action potential (ECAP). Therefore it is important to determine whether ECAP and psychophysical measures of channel interaction are related, and if these measures can be used to select optimal speech processing parameters on an individual basis. Specific experiments are designed to examine: (1) the relation between ECAP and psychophysical measures of channel interaction using a forward-masking technique, (2) the effects of stimulus duration on psychophysical forward masking and its relation to ECAP forward-masking measures, (3) physiologic and psychophysical measures of channel interaction with simultaneous stimulation, (4) the effect of phase on physiologic and psychophysical simultaneous channel interaction measures, (5) the relation between simultaneous and non-simultaneous channel interaction within subjects, and (6) the relation between channel interaction and speech perception ability with simultaneous and sequential speech processing strategies.

Families

Programming a cochlear implant (CI) speech processor requires the audiologist to choose from many different parameters in the programming software. Changes in these parameters can affect sound quality or overall speech perception performance with the CI. The programming process also requires active participation on the part of the CI recipient. This includes making judgments about the pitch or loudness of certain sounds on many different electrodes. This task can be difficult or impossible for infants, young children, or recipients with multiple disabilities. As a result, an extensive period of time could elapse before an optimal speech processor program is generated for an individual. Newer cochlear implants have special technology inside them that allows clinicians and researchers to quickly and easily measure the response of the hearing nerve to stimulation from the implant. These “objective” neural measures may be related to certain aspects of sound that recipients can describe, such as loudness, pitch, etc. (“behavioral” measures). The purpose of this research is to examine how certain behavioral measures are related to objective measures from the hearing nerve through the cochlear implant. We hope that this research will result in ways to use objective measures for choosing certain speech processing parameters, and reducing the amount of time needed to create an optimal program for both pediatric and adult CI recipients.

Professional Resources

Presentations

Specific Areas of Research:

Comparing physiologic and psychophysical measures of channel interaction using a forward-masking technique.
Examining the effect of stimulus duration on psychophysical forward masking.
Comparing physiologic and psychophysical measures of channel interaction with simultaneous stimulation.
Examining the effect of phase on simultaneous channel interaction measures.
Examining the relation between simultaneous and non-simultaneous channel interaction within subjects.
Examining the relation between channel interaction and speech perception ability with simultaneous and sequential speech processing strategies.