The Department of Communication Sciences and Disorders at the University of Iowa is one of the oldest in the United States. Although originally developed under Psychology around the 1930s, Speech Pathology and Audiology became an independent department in 1956, and moved into its current location in the Wendell Johnson Speech & Hearing building in 1967. This year, we became the Department of Communication Sciences and Disorders. The department has been ranked in the top 2 in the nation by US News and World Report magazine for several years. The Wendell Johnson Speech and Hearing Clinic has a history of excellence in the quality of clinical services provided to individuals with communication disorders and in the quality of clinical education offered to graduate students in speech pathology and audiology. Today the goal at Wendell Johnson Speech and Hearing Center is to build a future worthy of the past. Assessment and therapy are provided by graduate student-clinicians under the direct supervision of certified and licensed speech-language pathologists and audiologists.

Active research programs exist at The University of Iowa in all major areas of speech and hearing. Individual laboratories are maintained in the Wendell Johnson Speech and Hearing Center for the study of auditory physiology, auditory rehabilitation, clinical experimental and medical audiology, language disorders and intervention, neurology of speech and language, psychoacoustics, psycholinguistics, speech physiology, stuttering, and voice acoustics and biomechanics.

Today I will be highlighting four labs focusing on research in hearing: The Human Electrophysiology Lab, the Hearing Lab, the Auditory Research Lab and the Hearing Aid Lab.

The Human Electrophysiology Lab is codirected by Dr. Carolyn Brown and Dr. Paul Abbas. The mission of this lab is to explore innovative ways in which electrically evoked auditory potentials can be used either to facilitate management of the cochlear implant patient or to learn more about how electrical signals are processed within the brain. I’m going to show you here three different projects they are working on related to cochlear implants.

The first project I will talk about uses the Electrically-evoked Compound Action Potential (ECAP) to study how different electrodes on the cochlear implant may be interacting within the cochlea. Here you can see there is a probe electrode and the masking electrode that together produce an ECAP. By subtracting out the ECAP response to the probe alone, you get an idea of how much interaction was present. Electrodes closer to the probe have a greater interaction than electrodes farther away. The variability between users is great, and there seems to be no relationship between it and speech perception.

The lab is also studying how having 2 cochlear implants affects the electrically-evoked auditory brainstem response (EABR). In the past couple years, we have seen an increase in the number of adults and children receiving bilateral cochlear implants. One of the issues audiologists must face is programming the devices so that similar frequency regions of the cochlea are being stimulated in both ears to the same signal. Now binaural interaction components can be measured in response to stimulation from both implants. This response occurs at the excitatory/inhibitory cells of the lateral superior olivary complex. Seven adult bilateral cochlear implant users were tested. Responses from similar numbered electrode pairs were stronger than responses from different numbered electrode pairs. This suggests that matched stimuli yield a larger binaural interaction than unmatched stimuli. This information may be used to help ensure good electrode matching between implants.

Finally, this lab is studying the electrically evoked cortical change complex. This complex appears in response to an alteration in repeating stimuli and seems to be related to discrimination ability. By altering frequency, temporal or intensity characteristics within a stream of electrode activations, the alterations that generate an ECC are thought to be discriminable by the CI user; the alterations that do not generate an ECC are probably not discriminable.

The Hearing Lab headed by Dr. Christopher Turner is also doing research with cochlear implants. Currently they are investigating a short electrode cochlear implant (the Hybrid), meant to stimulate high frequency regions of the cochlea, but preserve low frequency hearing. Here you see the audiological criteria for fitting this type of implant. Here you can see the improvement in consonant recognition over time with the hybrid – notice that acoustic hearing has not degraded. A similar pattern occurs with place recognition (e.g., /p/ and /b/ are both bilabial). Preserving low frequency helps with understanding speech in noise better than with a long electrode. Notice that the hybrid performance is similar to a person with mild to moderate sensorineural hearing loss. Hybrid users also demonstrate much better music recognition than long electrode users.

I would like to talk to you now about the Auditory Research Lab which is headed by one of our newest faculty, Dr. Shawn Goodman. Dr. Goodman is interested in research around otoacoustic emissions as well as hearing aids. Dr. Goodman’s lab contains a sound-treated booth and research software for sound delivery and recording. Dr. Goodman has used synchronous averaging (a technique used to measure OAEs) to measure Internal Noise of hearing aids. As you can see from this graph, there is a lot of variability in the internal noise across hearing aids.

Finally, I am going to talk about the lab I’m a member of, headed by Dr. Ruth Bentler, whom you have already met. The Hearing Aid Lab is focused on evaluating amplification technologies for both efficacy and effectiveness. When we investigate Efficacy, we investigate how well the technology is doing what it is designed to do (e.g., reduce low frequency gain, decrease microphone sensitivity, etc.). When we investigate effectiveness, we investigate how well the technology actually benefits the user of the technology. Two technologies we are especially focused on currently are directional microphones and digital noise reduction. For instance, directional microphones have been shown to decrease microphone sensitivity for sounds coming from the rear, however, many adults do not prefer directional microphones and will instead select omnidirectional microphones if they hear circuit noise, or if they have good access to visual cues. Digital noise reduction has been shown to change the gain characteristics of the hearing aid, and we have found that children demonstrate better speech perception when digital noise reduction is turned on compared to when it is turned off.

Thank you for listening to my talk today. I may not be able to answer your questions, but I would be happy to try, as well as to give you any contact information for the labs represented here.