CENTRAL AUDITORY PROCESSING DISORDER (CAPD)

Four grants were awarded for research that will increase our understanding of the causes, diagnosis, and treatment of CAPD, an umbrella term for a variety of disorders that affect the way the brain processes auditory information. All four of our CAPD grantees are General Grand Chapter Royal Arch Masons International award recipients.

+ Kenneth Vaden, Ph.D.

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Medical University of South Carolina
Adaptive control of auditory representations in listeners with central auditory processing disorder

Central Auditory Processing Disorder (CAPD) is typically defined as impairment in the ability to listen and use auditory information because of atypical function within the central auditory system. The current study uses neuroimaging to characterize CAPD in older adults whose impaired auditory processing abilities could be driven by cognitive and hearing-related declines, in addition to differences in central auditory nervous system function. Functional neuroimaging experiments will be used to test the hypothesis that older adults with CAPD fail to benefit from top-down enhancement of auditory cortex representations for speech. In particular, activation of the adaptive control system in cingulo-opercular cortex is predicted to enhance speech representations in auditory cortex for normal listeners, but not to the same extent for older adults with CAPD. This project aims to develop methods to assess the quality of speech representations based on brain activity and characterize top-down control systems that interact with auditory cortex. The results of this study will improve our understanding of a specific top-down control mechanism, and examine when and how adaptive control enhances speech recognition for people with CAPD.

Research area: Speech Recognition; Neural Representations; Adaptive Control; Central Auditory Processing Disorder

Long term goal: The long term expected outcome from this line of research is to develop neural endophenotypes and methods to enhance characterization of CAPD. A control system that modulates auditory cortex activity could also provide a brain mechanism to guide future interventions.

Kenneth Vaden, Ph.D. earned his Ph.D. in Psychology at the University of CA, Irvine with dissertation research mentored by Dr. Greg S. Hickok, and his postdoctoral research was mentored by Dr. Mark A. Eckert at the Medical University of SC. As a Research Assistant Professor at the Medical University of SC, Dr. Vaden studies brain systems that support speech communication and how these change with age.

+ ANDREW DIMITRIJEVIC, PH.D.

Cincinnati Children's Hospital Medical Center
Sensory and Cognitive Processing in Children with Auditory Processing Disorders: Behavior and Electrophysiology

Central Auditory Processing Disorder (CAPD) can be defined as having a listening difficulty despite having normal hearing. One theory of CAPD is that this bottom-up processing isn’t working properly, a bit like listening to a de-tuned radio or TV. However, when the sound code reaches the cortex, it is mixed with a variety of signals from other systems, including vision, memory and attention. A second theory of CAPD is that the problem occurs at this level of mixing. In this ‘top-down’ theory, inappropriate control signals from high-level thinking systems, especially memory and attention, are thought to lead to misunderstanding of the code produced in the auditory system. Unfortunately, these two theories are difficult to tease apart. For example, a typical statement by a parent of a child with CAPD is that (s)he seems unaware when being spoken to. This could indicate poor listening due to inattention, or due to an inability to process speech sounds in the auditory system. Understanding which theory is correct may be important for treatment of CAPD. This research aims to tease apart these two theories by examining how the brain processes sound. One aspect of this research will examine how the brain encodes pitch and level fluctuations in sound. Both of these sound qualities are the “building blocks” of speech. If there are deficits at this level of neural processing then perhaps a “bottom up” or sound encoding problem exists. Another aspect of this research will examine a more cognitive approach and examine how the brain deals with speech in noise. This will be indexed by use of brain oscillations which are thought to reflect neural networks across different parts of the brain. Therefore by approaching CAPD from these two directions, it may be possible to show whether their listening difficulties are due to bottom-up or top-down processing problems.

Research Area: Electroencephalography, behavior, psychoacoustics, sensory processing, cognitive processing

Long term goal: This research addresses whether there are subtypes of Central Auditory Processing Disorder (CAPD), arising from deficits of bottom-up or top-down processing. Bottom-up processing refers to how the sound signal is encoded up to the level of the brain (i.e., ear to auditory nerve through the brainstem and up to the brain). Top-down processing is what the brain does with that information and includes cognition and attention. Understanding the mechanism of the CAPD will help direct clinicians as to what intervention may be most appropriate. For example, bottom-up problems may be best dealt with using a ‘communication device’. These resemble a cell phone ear piece and they are activated wirelessly by a small microphone worn by a teacher or parent. Top-down problems, on the other hand, may be better remedied by auditory training. Developing a test to tease apart these two scenarios and use this information to guide intervention is the long term goal of this project.

Andrew Dimitrijevic, Ph.D. received his Ph.D. at the University of Toronto working on auditory steady-state responses with Dr. Terrence Picton. He went on to do two postdoctoral fellowships, at University of British Columbia (with Dr. David Stapells) and at University of California Irvine (with Dr. Arnold Starr). He is currently at the Cincinnati Children’s Hospital and studies the electrophysiology of human hearing and development in children with auditory processing disorders, cochlear implants and single-sided deafness.

+ HARI BHARADWAJ, PH.D.

Massachusetts General Hospital
A systems approach to characterization of subcortical and cortical contributions to temporal processing deficits in central auditory processing disorders

Increasingly in the clinic, children report difficulty in understanding speech in the presence of other competing sounds. When these children are able to detect faint tones normally and show no classic signs of other neurological disorders, they are labeled as having Central Auditory Processing Disorder (CAPD). Understanding speech in a noisy setting is complex and relies both on the representation of subtle sound features by the auditory system, and the brain’s ability to make use of this information. Thus, difficulty can arise for a variety of reasons. Indeed, difficulty communicating in noisy settings is reported in a wide range of diagnostic categories such as Language Delays, Autism Spectrum Disorders, and Dyslexia among others. Yet, robust diagnostics that characterize CAPD – an auditory-specific disorder – as distinct from these other disorders are lacking. Here, we will use otoacoustic emissions and non-invasive brain imaging techniques (Electro/Magnetoencephalography) to passively measure how children’s inner ear, brainstem and cortex capture sound information. By examining the relationship between these measures and listening behavior, we aim to obtain a detailed objective test battery for the assessment of auditory function that would lead to novel clinical diagnostics for CAPD and provide clues for targeted intervention.

Research Area: Central Auditory Processing Disorders

Long term goal: This line of research seeks to achieve two parallel goals:

  1. To understand the physiological mechanisms that allow us to listen and communicate in noisy settings thereby illuminating why different groups of individuals have difficulty in such settings, and,
  2. To leverage this understanding to develop non-invasive objective tools that can be used in the diagnosis and stratification (“subtyping”) of a diverse yet overlapping setof communication disorders.

Hari Bharadwaj received his Ph.D. in Biomedical Engineering from Boston University and is currently a Research Fellow at Massachusetts General Hospital. Prior to that, he received his M.S. and B.Tech., both in Electrical Engineering, from University of Michigan and Indian Institute of Technology, respectively.

+ Beula Magimairaj, Ph.D.

University of Central Arkansas
Moving the science forward through interdisciplinary collaborative research integrating Hearing, Language, and Cognitive Science

Clinicians and researchers lack a consensual theoretical and clinical framework for conceptualizing Central Auditory Processing Disorder (CAPD) because professionals in different disciplines characterize it differently. Children diagnosed with CAPD may have deficits in attention, language, and memory, which often go unrecognized. There is a lack of a valid and reliable assessment tool that can characterize auditory processing, attention, language, and memory on the front-end. This project is an interdisciplinary effort to lay the foundation for such an assessment. Our goal is to develop an assessment that includes sensitive measures that can help build an initial profile of a child’s source(s) of difficulties that may be manifested as auditory processing deficits. During this 1-year project, computer-based behavioral tasks that integrate theoretical and methodological advances from the CAPD literature, and hearing, language, and cognitive science, will be developed. Tasks will be piloted on sixty typically developing children (7-11 years) who have no history of auditory processing/cognitive disorders for feasibility testing. Developing an assessment that will validly characterize the abilities of affected children is a multi-stage enterprise and this project is a critical first step.

Research Area: Central Auditory Processing Disorders

Long term goal: Clinicians lack a psychometrically sound assessment tool that can reliably characterize auditory processing and attention, language, and memory deficits that are known to frequently co-occur in children diagnosed with CAPD. Comprehensive assessment in all these areas is not feasible in a single assessment. In the long-term, the investigators aim to develop a sensitive and valid test that can serve as a front-end differential screening tool for children suspected to have CAPD. Guided by pilot data from the current project, future projects will extend the study to school-age children suspected to have CAPD. Future studies will establish test validity, reliability, normative data collection, and standardization. When developed, the assessment will serve as an important front-end tool for speech-language pathologists and audiologists for screening and for directing parents towards appropriate management resources. This preliminary testing can better inform further testing and possibly reduce misdiagnosis. Appropriate diagnosis of children suspected to have the complex condition known as CAPD, is the first step to providing helpful intervention. The development of a valid and reliable multi-disciplinary assessment will add to the growing research base regarding auditory function in children and how it relates to attention, memory, and language functioning.

Dr. Beula Magimairaj received a Ph.D. in Speech Language Science from Ohio University. She is also a clinically certified speech language pathologist. Dr. Magimairaj is currently Assistant Professor in Communication Sciences and Disorders at the University of Central Arkansas. Her research interests are in Specific Language Impairment and cognition, and include the study of children diagnosed with auditory processing disorders. Dr. Magimairaj's co-investigators on this grant are Dr. Natalie Benafield, Au.D. and Dr. Naveen Nagaraj, Ph.D., CCC-A.