By Beula Magimairaj, Ph.D.
Children suspected to have or diagnosed with auditory processing disorder (APD) present with difficulty understanding speech despite typical-range peripheral hearing and typical intellectual abilities. Children with APD (also known as central auditory processing disorder, CAPD) may experience difficulties while listening in noise, discriminating speech and non-speech sounds, recognizing auditory patterns, identifying the location of a sound source, and processing time-related aspects of sound, such as rapid sound fluctuations or detecting short gaps between sounds. According to 2010 clinical practice guidelines by the American Academy of Audiology and a 2005 American Speech-Language-Hearing Association (ASHA) report, developmental APD is a unique clinical entity. According to ASHA, APD is not the result of cognitive or language deficits.
In our July 2018 study in the journal Language Speech and Hearing Services in the Schools for its special issue on “working memory,” my coauthor and I present a novel framework for conceptualizing auditory processing abilities in school-age children. According to our framework, cognitive and linguistic factors are included along with auditory factors as potential sources of deficits that may contribute individually or in combination to cause listening difficulties in children.
We present empirical evidence from hearing, language, and cognitive science in explaining the relationships between children’s auditory processing abilities and cognitive abilities such as memory and attention. We also discuss studies that have identified auditory abilities that are unique and may benefit from assessment and intervention. Our unified framework is based on studies from typically developing children; those suspected to have APD, developmental language impairment, or attention deficit disorders; and models of attention and memory in children. In addition, the framework is based on what we know about the integrated functioning of the nervous system and evidence of multiple risk factors in developmental disorders. A schematic of this framework is shown here.
In our publication, for example, we discuss how traditional APD diagnostic models show remarkable overlap with models of working memory (WM). WM refers to an active memory system that individuals use to hold and manipulate information in conscious awareness. Overlapping components among the models include verbal short-term memory capacity (auditory decoding and memory), integration of audiovisual information and information from long-term memory, and central executive functions such as attention and organization. Therefore, a deficit in the WM system can also potentially mimic the APD profile.
Similarly, auditory decoding (i.e., processing speech sounds), audiovisual integration, and organization abilities can influence language processing at various levels of complexity. For example, poor phonological (speech sound) processing abilities, such as those seen in some children with primary language impairment or dyslexia, could potentially lead to auditory processing profiles that correspond to APD. Auditory memory and auditory sequencing of spoken material are often challenging for children diagnosed with APD. These are the same integral functions attributed to the verbal short-term memory component of WM. Such observations are supported by the frequent co-occurrence of language impairment, APD, and attention deficit disorders.
Furthermore, it is important to note that cognitive-linguistic and auditory systems are highly interconnected in the nervous system. Therefore, heterogeneous profiles of children with listening difficulties may reflect a combination of deficits across these systems. This calls for a unified approach to model functional listening difficulties in children.
Given the overlap in developmental trajectories of auditory skills and WM abilities, the age at evaluation must be taken into account during assessment of auditory processing. The American Academy of Audiology does not recommend APD testing for children developmentally younger than age 7. Clinicians must therefore adhere to this recommendation to save time and resources for parents and children and to avoid misdiagnosis.
However, any significant listening difficulties noted in children at any age (especially at younger ages) must call for a speech-language evaluation, a peripheral hearing assessment, and cognitive assessment. This is because identification of deficits or areas of risk in language or cognitive processing triggers the consideration of cognitive-language enrichment opportunities for the children. Early enrichment of overall language knowledge and processing abilities (e.g., phonological/speech sound awareness, vocabulary) has the potential to improve children's functional communication abilities, especially when listening in complex auditory environments.
Given the prominence of children's difficulty listening in complex auditory environments and emerging evidence suggesting a distinction of speech perception in noise and spatialized listening from other auditory and cognitive factors, listening training in spatialized noise appears to hold promise in terms of intervention. This needs to be systematically replicated across independent research studies.
Other evidence-based implications discussed in our publication include improving auditory access using assistive listening devices (e.g., FM systems), using a hierarchical assessment model, or employing a multidisciplinary front-end screening of sensitive areas (with minimized overlap across audition, language, memory, and attention) prior to detailed assessments in needed areas.
Finally, we emphasize that prevention should be at the forefront. This calls for integrating auditory enrichment with meaningful activities such as musical experience, play, social interaction, and rich language experience beginning early in infancy while optimizing attention and memory load. While these approaches are not new, current research evidence on neuroplasticity makes a compelling case to promote auditory enrichment experiences in infants and young children.
A 2015 Emerging Research Grants (ERG) scientist generously funded by the General Grand Chapter Royal Arch Masons International, Beula Magimairaj, Ph.D., is an assistant professor in the department of communication sciences and disorders at the University of Central Arkansas. Magimairaj’s related ERG research on working memory appears in the Journal of Communication Disorders, and she wrote about an earlier paper from her ERG grant in the Summer 2018 issue of Hearing Health.