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Kresge Hearing Research Institute

Department of Otolaryngology

Auditory Prosthesis Perception and Psychophysics Labs

Auditory Prosthesis Perception & Psychophysics Menu

Auditory Prosthesis Perception and Psychophysics Laboratories

Research

The goals of our research are to understand the mechanisms of electrically induced hearing and to identify ways to improve the function of auditory prostheses. To achieve these goals, we study functional (behavioral) responses to electrical stimulation under a variety of conditions. Our research focuses on independent variables that affect the spatial and temporal pattern of the neural response to electrical stimulation. These variables fall into two major categories:

  1. features of the electrical stimulus
  2. variables that affect the condition of the cochlea and the auditory pathway.

Features of electrical stimulation include electrode configuration placement and temporal features of the electrical waveform, such as phase duration, pulse rate, and pulse polarity order. Independent variables affecting the condition of the cochlea and auditory pathway include variables that induce deafness, duration of deafness and implantation, and electrical or chemical stimulation of the auditory system following the onset of deafness.

We study the functional effects of these independent variables in human and animal subjects. In humans, we measure effects of features of electrical and acoustic stimulation on speech perception and on psychophysical detection and discrimination thresholds. Parallel psychophysical studies are conducted using guinea pigs that are trained to perform detection and discrimination tasks using positive reinforcement operant conditioning. In collaboration with the laboratories of Drs. Bledsoe and Middlebrooks we also obtain neurophysiological data from these animals to determine the neural response patterns that are associated with detection and discrimination of the electrical stimuli.

Our collaborations with two additional research groups significantly enhance our research program. The Engineering Research Center for Development of Wireless Integrated Microsystems, directed by Dr. Kensall Wise, has chosen auditory prostheses as one of its major test beds. This program is concerned with development of stimulating electrode arrays, low power signal processors and wireless communication systems that are essential to advancing the field of auditory prostheses. This facility can provide the technology required for us to meet some of our research objectives and, in turn, we serve as a test bed for this new technology.

The tissue engineering research groups at the University of Michigan (Drs. Raphael, Altschuler, Miller, and colleagues) are developing procedures to enhance and control nerve survival patterns in the deafened cochlea and to regulate tissue growth in the implanted inner ear. These techniques provide us with tools for understanding the role of nerve survival patterns and tissue growth on cochlear implant function and our research, in turn, can help determine the efficacy of the tissue engineering procedures.

Data from these studies form the basis for models of the neural mechanisms underlying hearing with auditory prostheses. These models, in turn, are tested and refined by further behavioral and neurophysiological experiments. The data and models derived from these experiments are directly applicable to the design of auditory prosthesis electrode arrays and speech processing strategies.

This research is funded by grants from the National Institutes of Health and the National Science Foundation. Principal funding sources are listed below.