The ABCs of CAPD at ARC: An Interview with Frank Musiek, PhD
Academy Associate Editor Sumit Dhar spoke with Dr. Musiek about CAPD and this year's Academy Research Conference
The Academy Research Conference (ARC) has become the venue for a deep dive into a topic of current interest and controversy, the day before we start our exploration of all things audiology at AudiologyNOW! every year. This year's topic and controversy are old friends. Central auditory processing disorders or CAPD has been squarely in the audiology practice space for a while. The science behind CAPD was carefully and meticulously developed from the very first day. However, the condition has continued to be an enigma, resistant to be fully discovered.
There are many reasons why CAPD and ARC are the perfect match this year. Why not learn all about this from one of the original master's of this area of work, Dr. Frank Musiek. Dr. Musiek, currently at the University of Arizona, is one of the foremost scientists and clinicians in the general area of neuroaudiology and has taken the lead in organizing this year's ARC. We asked him about the why, what, and why now of this year's ARC.
Why CAPD at the ARC?
Well, Sumit, that is an easy question. The Academy Research Conference (ARC) at AudiologyNOW! 2016 is dedicated to bringing new research ideas to the forefront—especially those ideas that may translate to clinical application. The basic science underlying CAPD has always been strong, but recently has gained considerable research momentum and interest among clinicians and scientists. There have been many new innovations that have pointed to the central auditory nervous system as being responsible for many of the unanswered questions about hearing and its disorders that we have struggled with in the past. In addition, it appears that more and more of the advances in science are pointing towards the brain as being the key operator in many of the hearing processes we once thought were a domain of the peripheral auditory system. We also have many new researchers that are devoting their time and effort exclusively to investigating the central auditory nervous system. Also, clinicians are facing challenges of more patients in whom they identify central auditory nervous system disorders than ever before. All of these factors and probably many others certainly provide a great rationale for devoting the ARC conference this year to the research base of CAPD.
Individuals attending the ARC conference will hear about new research related to the central auditory nervous system and directly or indirectly to CAPD. We have an outstanding lineup of speakers who will be presenting the most recent basic and clinical research. We have Holly Fitch, a colleague of mine when I was at the University of Connecticut, who will relate current research on disorders of neurodevelopment and how this can affect auditory processing. Steve Lomber, of Western University (Canada), will talk about auditory cortex plasticity after incurring hearing loss. He is using cryoloop cooling to create reversible lesions, a unique research procedure that he will discuss. Jos Eggermont, from the University of Calgary, has a most interesting presentation on how long- duration, non-traumatic noise exposure can actually compromise function of the auditory cortex. These exposures are long-term but at levels most would expect not to affect the auditory system. Ken Hugdahl of the University of Bergen (Norway) brings his vast experience with dichotic listening to ARC, and as he has done in presentations around the world, he will provide an insightful view of his latest research. Kathy Pichora-Fuller of the University of Toronto, Mississauga will share her views on the interesting interactions between auditory and cognitive processing in the older adult population. Both Jeff Weihing of the University of Louisville and Harvey Dillon of the National Acoustic Laboratory (Australia) will discuss new approaches to auditory training for CAPD.
In addition, Sumit, we will have over 40 posters displayed throughout the day at the conference. The ARC committee is extremely pleased with the quality and scope of the research, as well as the interest expressed in sharing research at ARC, as reflected by the number of posters submitted. I am confident that the attendees will especially enjoy looking at this broad spectrum of research in the area of CAPD.
So, you see, Sumit, there is a lot of new information that will be available at the ARC conference.
There are a number of presentations involving animal research, could you comment on its relevance to CAPD?
Animal research has been an important underpinning to advances in our understanding of CAPD. For example, many years ago when Marilyn Pinheiro and I were working on the frequency pattern test, we were highly influenced by the animal research of Drs. Neff, Butler, and Diamond. Essentially, they showed that cats with ablation of their auditory cortex could not recognize auditory patterns, though before surgery they could perform these recognition tasks without difficulty. The results of this study was a primary impetus leading to the development and use of the frequency and duration pattern tests. As I mentioned earlier, Dr. Lomber currently uses the technique of cryoloop cooling to create lesions in the central auditory nervous system in animals. This lesion can be reversed to demonstrate the consequences of the lesion, as well as recovery patterns to baseline. This is a novel and much appreciated advance in animal research that will advance our understanding of central auditory processing and its disorders in humans. In fact, much of our current understanding of localization, temporal processing, auditory evoked potentials, and central auditory dysfunction can be traced back to animal research. Animal research, especially that dealing with lesion effects are, and will continue to be, critical to central auditory assessment and treatment and management of individuals with neurologically- based central auditory processing disorders.
Using that as a segue, I would like to mention the extremely important, but often overlooked aspect of CAPD, that of neurologically-based central auditory processing disorders. This population is terribly underserved by audiology. It is also a most interesting population from which we could probably learn the most. Audiology must move towards more involvement with the neurologic patient. Many of the tools are already in place to do this ---they simply are not being utilized. We must improve communication with our fellow neurologists and neurosurgeons so that we can serve appropriately individuals with auditory disorders that are neurological in nature.
What do we know about traumatic brain injury and chronic noise exposure contributing to CAPD?
Those are very good questions, Sumit. Traumatic brain injury or TBI is a neurologically-based central auditory disorder. This problem has been brought to our attention by the veterans returning from the Middle East with auditory symptoms, but normal audiograms. These individuals usually are exposed to some type of blast injury. Erick Gallun, at the Portland VA has done some nice work on central auditory assessment of these veterans exposed to blast injuries. Certainly some of these individuals, have central auditory deficits that can be shown quite clearly with a suitable test battery. One of the issues that is poorly understood is that we lack a reference to determine whether a given individual actually has incurred central auditory damage with TBI. Imaging does not really help much in this regard. Some people who have been exposed to blast injury may have incurred central auditory damage, but others may not have. This makes it difficult to quantify the sensitivity of central tests in identifying auditory deficits related to blast injury because we cannot be sure in which individuals the central auditory nervous system truly has been compromised. This is, for example, unlike individuals who may have incurred a stroke of Heschl's gyrus where we can be quite sure there is a known central auditory deficit because imaging can provide the site of involvement. Nonetheless, considerable progress has been made, and certainly individuals with TBI should be evaluated using a well-constructed central auditory test battery. TBI also has come to the forefront in relation to sports injuries; however, central auditory test data along these lines is just emerging.
Since Dr. Eggermont will discuss noise exposure and central effects, with an emphasis on non-traumatic levels of noise exposure, I will not comment much on this topic here. It is important to know, however, that traumatic levels of noise exposure do indeed result in central consequences, as reported a number of years ago. That research dates back to the early 1980s when legendary auditory neuro-anatomist Kent Morest presented and then published a paper entitled "Degeneration of the brain following exposure to noise." This investigation documented how central auditory structures in the brain stem pathway were damaged following noise exposure. This was one of the first reports demonstrating that noise exposure that damages the cochlea also damages the central system. Since that time, this finding has been reaffirmed and expanded upon by many investigators. Unfortunately, I would have to say that many clinicians still are unaware of the significance of this research. Hence, Dr. Eggermont's ARC presentation will be timely and relevant.
What will the ARC have for those of us practicing in general audiology and not at a clinic that specializes in CAPD?
Well, the presentations will make the participants aware of the many advances made in the underpinnings of CAPD. The presentations also will demonstrate the high level of basic science in the area of CAPD. Information at ARC will also show the increasing major role the central auditory system plays in hearing, a relationship that has been under appreciated by many clinicians for far too long. Also profiled in the program will be the limited role the pure tone audiogram plays in the comprehensive assessment of hearing--something of importance to all audiologists. Your readers may want to look at the January/February, (2016) issue of Audiology Today for "Perspectives on central auditory processing disorder" for more background on this topic.
The ARC CAPD program will make absolutely clear the role of central auditory function and the consequences of its related disorders. I also strongly believe that after attending this conference, many audiologists who do not currently evaluate nor treat CAPD will logically ask themselves –why not? ARC will provide insight to the basic physiological mechanisms involved in auditory processing that will better enable the audiologist, even those who do not have a CAPD practice, to identify centrally generated symptoms so that appropriate referrals can be made.
Finally, with great speakers and topics, all who attend will be fascinated and intrigued by the information presented.
Thank you, Dr. Musiek for taking the time to lift the curtain on this year's Academy Research Conference (ARC), just a little bit. There appear to be many more thrills that are behind these curtains. It is remarkable how often we forget that we provide care for the entire hearing system and not just the cochlea. This year's ARC will help us reconnect with the whole system and learn about the interdependency between the different layers of auditory anatomy. We were excited about this year's ARC already. Now, we just cannot wait.