Research

Cochlear Implant NIH Research Grant

The Iowa Cochlear Implant Project at The University of Iowa under the direction of Bruce Gantz, MD, professor and head of otolaryngology, is supported by a $10 million grant from the National Institute on Deafness and Other Communication Disorders (NIDCD). This is the fourth NIDCD grant that the Iowa Cochlear Implant Program has received from the National Institutes of Health.

Grant funds allow researchers to continue to identify the factors that determine why some individuals benefit to a greater extent from the implant than others. In addition, researchers work to determine whether two implants enable the user to hear better than one; to develop and evaluate new signal processing for speech perception and music appreciation; and to study the expansion of selection criteria, including adults with more hearing, and to track the benefit of early implantation in infants.

Interrelated research projects address the goals of this project:

• Binaural Signal Processing in Adults and Children
• Audiology and Signal Processing in Children
• Electrophysiology
• Music Perception
• Speech Production and Language Development

Binaural Signal Processing in Adults and Children
Directed by Richard Tyler, PhD

This project addresses issues related to cochlear implantation using audiological and speech-perception techniques. With regard to adults, individuals with more residual hearing will receive cochlear implants to determine if the current selection criteria can be broadened to benefit more patients. In addition, speech perception measures will be collected to document the use of novel signal processing (i.e., bilateral cochlear implants, combined acoustical and electrical signals, high-rate signal processing). Finally, the effects of aging on the speech perception abilities of older cochlear implant recipients will be studied. With regard to children, the bilateral benefits of using a cochlear implant and a hearing aid on opposite ears will be studied.

Audiology and Signal Processing in Children
Directed by Carolyn Brown, PhD

In our effort to further define appropriate selection criteria in very young children, a computer-based, visual reinforcement audiometry system will be used to measure a head-turn preference response, and a split-screen, preferential looking response in children younger than 12 months of age. These findings will be compared to play audiometry thresholds collected on these same children at a later age. To further explore which children should get a cochlear implant, the speech perception of hearing-impaired, school-aged children using well-fit hearing aids will be collected.

Electrophysiology
Directed by Paul Abbas, PhD, and Carolyn Brown, PhD

This project addresses five specific areas related to cochlear implantation using electrophysiological techniques. The first aim is to evaluate methods for establishing cochlear implant candidacy in very young children, specifically by using auditory steady-state evoked potentials. The second aim will assess the use of physiologic measures to determine levels used to program the speech processor, specifically for very young children. The third aim will evaluate the effects of residual hearing on electrically evoked responses. This patient population will primarily consist of individuals who have received an investigational device equipped with a short electrode array designed to preserve residual acoustic hearing. The fourth research aim addresses the use of physiologic measures to identify signal processing parameters that might be changed in order to optimize speech perception with the cochlear implant. The last research aim will document long-term changes (or stability) in physiologic measures made in children and adults.

Music Perception
Directed by Kate Gfeller, PhD

Music is a common part of cultural rituals, social events, and is valued for its artistic and emotional expression. Following speech perception, music appreciation is the next most commonly expressed desire of implant recipients. However, current devices and coding strategies have been designed with speech perception in mind. Implant recipients commonly describe the sound of music through current implants as unnatural or unpleasant in quality, and find tasks requiring good pitch perception (e.g., song recognition) very difficult. This project will investigate several novel signal-processing schemes to determine if music perception and appreciation can be enhanced. We will also examine the relations among psychophysical, psychological, and speech perception measures, and perception of complex musical sounds. Past research indicates that systematic training can improve some aspects of music appreciation, even for implant recipients who use current speech processors. We will examine the effect of systematic training versus long-term use for implant recipients who use conventional speech processing strategies as well as novel signal processing that has been optimized for music listening. Because we have a large group of implanted children who are long-term users, we can follow changes in music perception and appreciation that occur as a result of experience with the device over time and can compare the music perception of our prelingually deafened young adults to postlingually deafened adults. Finally, we will follow changes in auditory perception in infants, young children who use cochlear implants, and children who use conventional hearing aids.

Speech Production and Language Development
Directed by Bruce Tomblin, PhD

Research has shown that implantation of congenitally deaf children accelerates their development of speech-based communication. Theories of speech and language development predict that earlier implantation should provide improved benefits for speech and language development, and also, that growth in speech and language development should be constrained as the child approaches adolescence. To test this, we will evaluate several measures of speech, language, and auditory perception in infants who use hearing aids, children implanted between 12- and 36-months of age, and children and/or adolescents with at least 10 years of cochlear implant experience. The benefits of implantation on speech and language development also result in a prediction that there will be subsequent gains in reading and general scholastic achievement among these children. Early reading achievement in second grade and later reading and scholastic achievement in 10th grade will be examined. Finally, achievement levels of speech and language development among implant users appears to exceed that found in many children with more acoustic hearing who wear hearing aids. A cross-sectional design will compare school-age implant users with age-mates who are hearing aid users. It is predicted that implant users will have better speech, language, and literacy levels than hearing aid users with low audibility levels, and that they will approach performance levels of their hearing peers.