Since 2005, the Marion Downs Lecture in Pediatric Audiology has been the highlight for pediatric audiologists attending AudiologyNOW!, the annual convention of the American Academy of Audiology. This lecture series is supported with a grant from The Oticon Foundation. The inaugural lecture was given by Anu Sharma, PhD. Many pediatric audiologists, myself included, can remember sitting in that session, captivated and inspired by the groundbreaking work that Dr. Sharma presented on the biological markers of auditory development and the impact of early intervention. This year, the Academy of Audiology Foundation (the Foundation) is honored to invite Dr. Sharma back this year to present the lecture at AudiologyNOW! 2017 in Indianapolis, Indiana, on Friday, April 7 at 9:45 am.
Dr. Anu Sharma is professor and interim chair of the Department of Speech Language and Hearing and a fellow at the Institute for Cognitive Science and Center for Neuroscience at the University of Colorado at Boulder. She also serves as an adjunct professor in the Department of Otolaryngology and Audiology at the University of Colorado at the Denver Medical School. Her research is focused on examining brain plasticity in children and adults with hearing loss who receive intervention with hearing aids and cochlear implants. Her research has been funded by the U.S. National Institutes of Health (NIH) since 2001.
In addition to her inaugural Marion Down’s lecture at AudiologyNOW!, Dr. Sharma has earned an international reputation as an eloquent speaker who can make her research understandable to any audience. She has given the keynote address at the British Academy of Audiology, the British Society of Audiology, and has presented at many other national, regional, and state venues. The Foundation is beyond pleased that she was available for the 2017 Marion Downs Lecture. I had the privilege to interview Dr. Sharma about her work since that inaugural lecture in 2005.
Eileen Rall: How did Dr. Downs inspire you all of those years ago?
Anu Sharma: Everything about Marion was and continues to be inspirational. The breakthroughs she made in pediatric audiology were extraordinary, especially at a time when women were hardly represented in important decisions in the field. Universal Newborn Hearing Screening would not have been conceptualized without the pioneering work of Marion.
I was also inspired by Marion personally. She lived her life to the fullest. I very much enjoyed reading her memoir called, “Shut up and Live!” She was always ahead of the curve. I recall that when I moved to Colorado to join the faculty at University of Colorado, one of the first emails I received was from Marion. In it, she linked some brand-new articles in pediatric neuroscience and asked if I had read them. She was probably 92–93 years old at that time, and that’s how on top of things she was!
What did it mean to you to be the first speaker for the Marion Downs Pediatric Lecture?
Especially since I had only been conducting pediatric research for 10 years, it was an incredible honor to be the first Marion Downs Lecture speaker. I still vividly remember the event. The questions and feedback I received were very insightful and helped inform my research in following years.
I remember sitting in the audience in awe of the research your lab was conducting. Was there any audience member follow-up that stays with you?
Thanks for the kind comment. I must acknowledge all of my students (past and present) who have worked so hard in the lab to allow us to have the findings we do. As I said, I very much enjoyed the interaction with the audience at the end of the first Marion Downs Lecture. The insightful comments and questions allowed me to think in different ways about our research findings and informed aspects of our future clinical studies.
Who are the researchers in pediatric hearing that you admire?
Marion Downs, of course! I also admire current pediatric research in areas including basic neurophysiology and clinical outcomes with hearing aids and cochlear implants. Importantly, these outcomes are not just restricted to speech and language development, but are encompassing social-emotional development and considering the child as a whole.
In the years since your first Marion Downs Lecture, what do you feel is the most significant advance we have made in pediatric hearing assessment and intervention?
As a field, we have made important strides in better understanding the variability underlying outcomes for children with hearing loss. For example, NIH-funded studies, e.g., The Childhood Development After Cochlear Implantation (CDACI), Outcomes for Children with Hearing Loss (OCHL), and The Longitudinal Outcomes of Children with Hearing Impairment (LOCHI), that you heard about last year when Dr. Teresa Ching was the invited presenter for the Marion Downs Lecture, are excellent examples of this kind of work.
The CDACI has shown so many important factors related to outcomes in children with cochlear implants that weren’t even considered 15 years ago, such as maternal education. We were so focused on variables such as the type of implant or amplification, measures we could control as audiologists. We learned from these studies to consider the whole child, the family situation, and the support from the community. You could have the perfect cochlear implant or hearing aid fitting and yet there is still so much variability in outcome if you didn’t consider the whole child.
Both you and last year’s lecturer, Dr. Teresa Ching, stress the value of measuring cortical auditory-evoked potentials (CAEPs) as a way of determining candidacy for technology or as a measure of the impact of intervention. Have you been able to implement this in any clinical protocols in the facilities where you work?
We have been measuring CAEPs for the better part of two decades. We did it clinically when I was at the University of Texas at Dallas, Callier Center, on almost every child that was a candidate for cochlear implantation, and they continued to do so for many years after I left. The focus of my work in Colorado is research, but I do offer P1 biomarker evaluations in my lab at no charge if cases are referred to us by audiologists after detailed consulting with us. We have had patients fly in from all over North America for the assessments. We try to focus our work on the most complex cases, such as those patients with auditory neuropathy spectrum disorder (ANSD), including hypoplastic auditory nerves, or children with co-morbid multiple disabilities that make behavioral assessment to help determine candidacy for cochlear implantation difficult. Measuring CAEPs gives you a functional assessment, whereas MRI is a structural assessment. I have publications of several case studies where we assessed CAEPs on children who had hypoplastic nerves to see if they were candidates for cochlear implantations, complex cases of ANSD, and on children with co-morbid disabilities (Roland et al, 2012; Sharma et al, 2013; Cardon et al, 2012).
With all of the benefits to doing CAEPs, what do you think is the barrier to wide-spread use of this tool clinically?
I think there are a couple of factors. First is training. We are probably still not training AuD students as much as we should on cortical potentials. Another is resources. To be candid, audiologists sometimes work under tight conditions where they don’t have the financial flexibility to add another test that requires additional equipment and training. Finally, measuring CAEPs in patients with cochlear implants can be challenging because of the cochlear implant artifact. It can be difficult to manage or minimize in the measurement, and you need a good understanding of it so it doesn’t ruin your data.
In a recent article you authored, you discuss the use of inter-trial coherence (ITC) as a more effective measure of function in patients with ANSD – can you tell us more about this measure and its clinical feasibility?
It’s a fairly new test. Typically, in auditory brainstem response (ABR) and CAEPs, we are measuring a timed waveform. We evaluate when the response is occurring. We can also look at cortical potentials and measure them in the frequency domain. This is a whole new area of cortical potentials that is opening up called “time frequency analysis.” There is so much rich information about the brain in the cortical potential, but typically we only consider the time aspect of it. Now we want to see the frequency aspect of it. To me, it was intuitive that we would want to use this type of analysis in patients with ANSD because ITC measures cortical synchrony through phase-locking. We found some very interesting results in which this analysis classified the patients into having good or poor synchrony, and it was measurable. The measure is more widely used in neuroscience literature, but there is very little clinical documentation of it in the CAEPs literature in audiology (Nash-Kille and Sharma, 2014; Sharma and Cardon, 2015).
In the article, you describe this measure as using a single impulse as opposed to relying on averaging responses over time. Is that correct?
Yes, you can think of it as presenting many iterations of a stimulus such as “bah, bah, bah, bah.” Every time you present a stimulus like that, you get a response from the brain. In typical cortical potentials, we just average it but in ITC we measure the response to each trial and then we see how coherent the response is across trials. Even children with ANSD who had a normal average P1 response, normal cortical potential, showed a deficit in this synchrony. It is a much more sensitive measure than the averaged response, at least in auditory neuropathy. We published a case study of a girl with unilateral ANSD. One ear was fine: it had a very synchronous response. In the other ear, sometimes we would present the stimulus and get a response from the brain and other times we wouldn’t. Given this degree of variability, it would be hard to make sense of our auditory world. The sound has to be consistent in its representation on the brain. If the signal coming in is not coherent, or synchronous, it is challenging to learn (Nash-Kille et al, 2014).
In another recent article on cortical development and neuroplasticity in ANSD, you report the impact of inconsistent or degraded stimulation on development. You reference the literature on deprivation due to chronic otitis media with effusion and the impact it has on auditory processing. Do you feel that this also applies to inconsistent use of amplification?
Absolutely, I do think inconsistent use of technology is a factor in outcomes. Our data in cochlear implants show us a clear pattern of changes in cortical potentials following implantation. When we would find a case in which development of the cortical potential wasn’t meeting its benchmarks, we could predict the inconsistent use of the technology as the reason for the lack of development. In those cases, when we do not see the changes in the brain’s response, we could follow up with the families and present the data to help support more consistent use. The brain’s responses were objective and very compelling and helped change behaviors. It was a very powerful counseling tool.
In your recent article, “Developmental and Cross-Modal Plasticity in Deafness: Evidence from the P1 and N1 Event Related Potentials in Cochlear Implanted Children,” you introduce the reader to “cross-modal plasticity” (CMP). Can you explain what cross-modal plasticity is and why the measurement of it is important in assessing outcomes for children with hearing loss?
CMP is a form of cortical re-organization associated with deafness. This form of plasticity occurs when an intact sensory modality recruits cortical resources from a deprived sensory modality to increase the processing capabilities of the intact modality. This recruitment appears to reverse in some cases following stimulation of the deprived sensory modality. Compensatory cross-modal re-organization, which results in areas of auditory cortex being re-purposed by vision or somatosensation, has been implicated as a factor that may further explain some of the variable outcomes in children with cochlear implants. Large-scale studies are needed to determine the extent to which cross-modal re-organization may be a predictive factor in pediatric cochlear implant success. We have a recent publication exploring cross-modal plasticity in children with cochlear implantation, and I will explore this topic in more detail in my presentation this April at AudiologyNOW! 2017.
In another article, “Cross-Modal Plasticity in Developmental and Age-Related Hearing Loss: Clinical Implications,” you discuss the reversal of cross-modal plasticity in a young child with progressive single-sided deafness (SSD) who received a cochlear implant. Have you seen any other cases of this? Is this something your lab is working on with pediatric patients?
Yes, we are very excited about looking at patients with SSD. We see the reversal in some of these patients. It depends on many factors such as age of hearing loss onset or implantation. Our lab has been interested in cross-modal plasticity not just in the pediatric population but also in age-related hearing loss. We are seeing cross-modal reorganization, recruitment by vision, in people with mild, early stage hearing loss. Interestingly, we have found in a couple of cases with well-fit amplification, there is reversal of the re-organization. These brain changes are happening in older adults as well as pediatric patients. We don’t take mild hearing loss as seriously as more significant degrees of hearing loss, yet we are seeing some of these same changes with deprivation or degradation. The brain is telling us a story that we need to listen to about compensatory plastic changes which happen secondary to hearing loss in both children and adults (Glick and Sharma, in press, and Sharma et al, 2016).
Last year at AudiologyNOW! in the Hearing Aids in Review session, Catherine Palmer said, “There is nothing mild about mild hearing loss.”
That is exactly right. Even mild degradation of the signal can impair development and processing. Cross-modal plasticity and markers of listening effort are showing us the impact of mild hearing loss and the benefits of intervention.
You will have 90 minutes to convey the results of your research to the audience at the 2017 Marion Downs Lecture. What lessons have you learned over the past decade that you want the readers of this article to take away that you won’t be able to cover in your lecture in Indianapolis?
I will try to be comprehensive, but I probably won’t be able to get to the case study level that would demonstrate the everyday clinical implications of the research. I want listeners to go read the papers so that they can apply the principles of brain plasticity in helping their patients.
Thank you for speaking with me, Dr. Sharma, and for giving us a preview of the 2017 Marion Downs Lecture in Pediatric Audiology. As a clinician for almost 30 years with a long-term focus on serving pediatric patients and their families, it is so meaningful to see the outcomes of what you do, and know that these outcomes are based on objective data and meticulous study methods. We hope that your research will one day become fully implemented in all facilities where pediatric patients are evaluated and treated so that early, accurate diagnoses are made and individualized treatment plans start as soon as possible.
Your lecture years ago was so memorable. Your enthusiasm for your research is contagious! I think I speak for many pediatric audiologists when I say we are grateful for your work and we look forward to learning more from you in Indianapolis.
Cardon G, Campbell J, Sharma A. (2012) Plasticity in the developing auditory cortex: evidence from children with sensorineural hearing loss and Auditory Neuropathy Spectrum Disorder. J Am Acad Audiol 23(6):396–411.
Glick H, Sharma A. (in press-epub online) Cross-modal plasticity in developmental and age-related hearing loss: clinical implications. Hear Res.
Nash-Kille A, Gilley P, Sharma A. (2014) Cortical organization and variability in unilateral auditory neuropathy spectrum disorder: a case study. Hear Bal Comm 2(1):41–51.
Nash-Kille A, Sharma A. (2014) Inter-trial coherence as a marker of cortical phase synchrony in children with sensorineural hearing loss and auditory neuropathy spectrum disorder fitted with hearing aids and cochlear implants. Clin Neurophys 125(7):1459–1470.
Roland P, Martin K, Booth T, Campbell J, Sharma A. (2012) Assessment of cochlear implant candidacy in patients with cochlear nerve deficiency using the P1 CAEPs biomarker. Coch Imp Inter 13(1):16–25.
Sharma A, Campbell J and Cardon G. (2015) Developmental and cross-modal plasticity in deafness: Evidence from the P1 and N1 event-related potentials in cochlear implanted children. Intl J Psychophys.
Sharma A, Cardon G. (2015) Cortical development and neuroplasticity in auditory neuropathy spectrum disorder. Hear Res.
Sharma A, Glick H, Campbell J and Biever A. (2013) Central auditory development in children with hearing loss: clinical relevance of the P1 CAEPs biomarker in hearing-impaired children with multiple disabilities. Hear Bal Comm 11(3).
Sharma, A, Glick, H, Campbell, J, Torres, J, Dorman, MF, Zeitler, DM. (2016) Cortical Plasticity and reorganization in pediatric single-sided deafness pre- and post-cochlear implantation: a case study. Otol Neurotol 37(2):E26–34.