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Frontiers of auditory prosthesis research: Implications for clinical practice
Hearing Research 242 (2008) 1–2
Contents lists available at ScienceDirect
Hearing Research journal homepage: www.elsevier.com/locate/heares
Editorial
Frontiers of auditory prosthesis research: Implications for clinical practice
Guest Editor Auditory prostheses have made remarkable progress in the last thirty years, restoring the ability to communicate aurally to over 120,000 severely hearing-impaired patients. They are by far the most successful neural prostheses in existence. However, significant additional improvements are still needed. There is substantial variation among patients in the benefits received from the prostheses and the causes of that variation are still poorly understood. Many patients complain of difficulties with aural communication in noisy environments and most report that their perception of music is unsatisfactory. There are currently many active research programs aimed at better understanding the function of auditory prostheses and at improving performance with these devices. The objective of this special issue of Hearing Research is to review progress on each of a number of specific auditory-prosthesis research topics and discuss the implications of this research for clinical practice. Each of the articles in this issue was specifically solicited with these objectives in mind. All of the submitted manuscripts underwent the standard peer-review process. The topic areas covered in this issue are outlined in the Table of Contents on the back cover. We begin with an overview by Wilson and Dorman which summarizes the history of auditory prosthesis development and discusses current strengths and weaknesses of auditory prostheses. We then consider a variety of specific research areas that offer promise for significantly improving the perception and communication skills of patients who use auditory prostheses. The first area concerns the design of implants that are used to stimulate and record from auditory neurons. Thin-film multichannel electrode arrays for the scala tympani (Wise and colleagues) and more central placements in the auditory pathway (Anderson) offer many potential advantages over the current commerciallymanufactured auditory prosthesis electrode arrays including higher contact density, more flexible design geometries, built-in position sensing and control mechanisms, on-board processing, and economical mass production. The article by Richter and colleagues considers optical stimulation as an alternative to the conventionally used electrical stimulation. Neural recordings from penetrating multichannel implants in the CNS have also played a major role in developing the understanding of auditory system function that underlies the design of auditory prostheses and in assessing the neural responses to auditory prosthetic stimulation. This work is detailed in the articles by Anderson, Lim and colleagues, Middlebrooks and Snyder and others. In addition to work on cochlear implants, we also review research on more central placements of auditory prosthesis stimulat0378-5955/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.heares.2008.06.006
ing electrode arrays including penetrating arrays in the auditory nerve (Middlebrooks and Snyder), cochlear nucleus (McCreery), and inferior colliculus (Lim and colleagues). Placement of electrode arrays central to the scala tympani is sometimes needed for patients whose pathology precludes the use of cochlear implants. However, these placements also offer some broadly applicable advantages such as better spatial resolution due to placement of electrodes in close proximity to the neural targets and direct access to healthier populations of neurons. The quality of information received from an auditory prosthesis depends on both the way in which the information is delivered and the condition of the neurons receiving the stimulation. The pathology of severe hearing impairment inevitably includes pathology and/or reorganization of the neurons that are intended to receive the input from auditory prostheses. Therefore, the research directed at improving the function of auditory prostheses includes efforts to improve the condition of the target neurons, especially spiral ganglion cells. The articles by Leake and colleagues and Shepherd and colleagues discuss effects of neurotrophins and/or electrical stimulation on preservation of auditory neurons in developing and mature animals respectively. The article by Altshuler and colleagues discusses the emerging technology of using stem cells to replace degenerated auditory neurons. Methods for delivering pharmaceuticals and cells safely and effectively to the inner ear and central auditory sites are themselves important topics of research and these are discussed by Hendricks and colleagues. Improvements in stimulation strategies over the last thirty years have resulted in very significant improvements in speech recognition performance by people using auditory prostheses (see review by Wilson and Dorman). The section of this issue on ‘‘features of stimulation” begins with a review of research on the relative importance of spectral and temporal cues for speech recognition and their interactions (Xu and Pfingst). We then review research on several innovative approaches to prosthetic stimulation including current focusing and steering techniques (Bonham and Litvak), experiments with asymmetric pulses (van Wieringen and colleagues), and the use of combined acoustic and electrical stimulation (Turner and colleagues). The design of rehabilitation strategies for individual patients with auditory prostheses requires measurement tools to assess the mechanisms underlying good and poor performance and the locus of problem areas. In this issue, we consider research assessing implant function at the psychophysical (Pfingst and colleagues) and electrophysiological (Miller and colleagues) levels. Finally, there is good evidence that cognitive factors play a significant role in the ability of patients to use auditory prostheses and that patients
2
Editorial / Hearing Research 242 (2008) 1–2
can benefit from training. Research on effective training procedures is reviewed in the article by Fu and Galvin. The articles presented in this series demonstrate that there are many active and exciting research areas that promise further improvements in an already miraculously effective treatment for severe hearing impairment. I thank the authors of these articles for their reviews of their own and other outstanding research strategies and results. I also thank the reviewers of these articles for their careful reading, critical reviews, and many helpful suggestions. Finally, I express appreciation to the National Institute on Deafness and Other Communication Disorders as well as other government institutions and private foundations for their ongoing support of re-
search on auditory prostheses and to the many research personnel and research subjects who make this work possible. Guest Editor Bryan E. Pfingst Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan Health System, Ann Arbor, MI 48109-5616, USA E-mail address: bpfi[email protected] Available online 22 June 2008
Contents lists available at ScienceDirect
Hearing Research journal homepage: www.elsevier.com/locate/heares
Editorial
Frontiers of auditory prosthesis research: Implications for clinical practice
Guest Editor Auditory prostheses have made remarkable progress in the last thirty years, restoring the ability to communicate aurally to over 120,000 severely hearing-impaired patients. They are by far the most successful neural prostheses in existence. However, significant additional improvements are still needed. There is substantial variation among patients in the benefits received from the prostheses and the causes of that variation are still poorly understood. Many patients complain of difficulties with aural communication in noisy environments and most report that their perception of music is unsatisfactory. There are currently many active research programs aimed at better understanding the function of auditory prostheses and at improving performance with these devices. The objective of this special issue of Hearing Research is to review progress on each of a number of specific auditory-prosthesis research topics and discuss the implications of this research for clinical practice. Each of the articles in this issue was specifically solicited with these objectives in mind. All of the submitted manuscripts underwent the standard peer-review process. The topic areas covered in this issue are outlined in the Table of Contents on the back cover. We begin with an overview by Wilson and Dorman which summarizes the history of auditory prosthesis development and discusses current strengths and weaknesses of auditory prostheses. We then consider a variety of specific research areas that offer promise for significantly improving the perception and communication skills of patients who use auditory prostheses. The first area concerns the design of implants that are used to stimulate and record from auditory neurons. Thin-film multichannel electrode arrays for the scala tympani (Wise and colleagues) and more central placements in the auditory pathway (Anderson) offer many potential advantages over the current commerciallymanufactured auditory prosthesis electrode arrays including higher contact density, more flexible design geometries, built-in position sensing and control mechanisms, on-board processing, and economical mass production. The article by Richter and colleagues considers optical stimulation as an alternative to the conventionally used electrical stimulation. Neural recordings from penetrating multichannel implants in the CNS have also played a major role in developing the understanding of auditory system function that underlies the design of auditory prostheses and in assessing the neural responses to auditory prosthetic stimulation. This work is detailed in the articles by Anderson, Lim and colleagues, Middlebrooks and Snyder and others. In addition to work on cochlear implants, we also review research on more central placements of auditory prosthesis stimulat0378-5955/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.heares.2008.06.006
ing electrode arrays including penetrating arrays in the auditory nerve (Middlebrooks and Snyder), cochlear nucleus (McCreery), and inferior colliculus (Lim and colleagues). Placement of electrode arrays central to the scala tympani is sometimes needed for patients whose pathology precludes the use of cochlear implants. However, these placements also offer some broadly applicable advantages such as better spatial resolution due to placement of electrodes in close proximity to the neural targets and direct access to healthier populations of neurons. The quality of information received from an auditory prosthesis depends on both the way in which the information is delivered and the condition of the neurons receiving the stimulation. The pathology of severe hearing impairment inevitably includes pathology and/or reorganization of the neurons that are intended to receive the input from auditory prostheses. Therefore, the research directed at improving the function of auditory prostheses includes efforts to improve the condition of the target neurons, especially spiral ganglion cells. The articles by Leake and colleagues and Shepherd and colleagues discuss effects of neurotrophins and/or electrical stimulation on preservation of auditory neurons in developing and mature animals respectively. The article by Altshuler and colleagues discusses the emerging technology of using stem cells to replace degenerated auditory neurons. Methods for delivering pharmaceuticals and cells safely and effectively to the inner ear and central auditory sites are themselves important topics of research and these are discussed by Hendricks and colleagues. Improvements in stimulation strategies over the last thirty years have resulted in very significant improvements in speech recognition performance by people using auditory prostheses (see review by Wilson and Dorman). The section of this issue on ‘‘features of stimulation” begins with a review of research on the relative importance of spectral and temporal cues for speech recognition and their interactions (Xu and Pfingst). We then review research on several innovative approaches to prosthetic stimulation including current focusing and steering techniques (Bonham and Litvak), experiments with asymmetric pulses (van Wieringen and colleagues), and the use of combined acoustic and electrical stimulation (Turner and colleagues). The design of rehabilitation strategies for individual patients with auditory prostheses requires measurement tools to assess the mechanisms underlying good and poor performance and the locus of problem areas. In this issue, we consider research assessing implant function at the psychophysical (Pfingst and colleagues) and electrophysiological (Miller and colleagues) levels. Finally, there is good evidence that cognitive factors play a significant role in the ability of patients to use auditory prostheses and that patients
2
Editorial / Hearing Research 242 (2008) 1–2
can benefit from training. Research on effective training procedures is reviewed in the article by Fu and Galvin. The articles presented in this series demonstrate that there are many active and exciting research areas that promise further improvements in an already miraculously effective treatment for severe hearing impairment. I thank the authors of these articles for their reviews of their own and other outstanding research strategies and results. I also thank the reviewers of these articles for their careful reading, critical reviews, and many helpful suggestions. Finally, I express appreciation to the National Institute on Deafness and Other Communication Disorders as well as other government institutions and private foundations for their ongoing support of re-
search on auditory prostheses and to the many research personnel and research subjects who make this work possible. Guest Editor Bryan E. Pfingst Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan Health System, Ann Arbor, MI 48109-5616, USA E-mail address: bpfi[email protected] Available online 22 June 2008