BACK TO AUDITORY PROCESSING DISORDER OVERVIEW

The National Center for Learning Disabilities lists four types of auditory skills essential to processing what one hears:

  1. Auditory discrimination is the ability to notice, compare, and distinguish the distinct and separate sounds in words. If a child has difficulty with auditory discrimination, he or she may confuse similar words like seventy and seventeen, have trouble learning to read, and be unable to follow directions even when the child appears to be paying attention.
     
  2. Auditory figure-ground discrimination is the ability to pick out important sounds from a noisy background. A child who struggles with auditory figure-ground discrimination may be unable to filter background conversations and noises to focus on what is important. For example, a child may miss lessons in class if he or she cannot filter extraneous background noise in the classroom.
     
  3. Auditory memory is the ability to recall what is heard after a period of time and includes both short-term and long-term memory. Difficulties associated with auditory memory may include remembering people’s names, memorizing telephone numbers, following multi-step directions, and recalling stories or songs.
     
  4. Auditory sequencing is the ability to understand and recall the order of words. Difficulties with auditory sequencing may include confusing numbers like 93 for 39 and confusing lists and sequences. For example, a child with auditory sequencing problems may not be able to complete a series of tasks in the right order. He or she may fail to be able to do so even when appearing to have heard and understood the directions.

Source: Brain Balance Achievement Centers

BACK TO AUDITORY PROCESSING DISORDER OVERVIEW

There are many behaviors that may point to APD.

Individuals with APD demonstrate a poor ability to:

  • Direct or divide attention
  • Discriminate subtle differences in sounds and words
  • Read, spell, write, understand vocabulary, or learn a foreign language
  • Understand rapid speech
  • Hear in noisy, social environments
  • Recognize and integrate a sequence of sounds into words or other combinations
  • Remember and/or comprehend spoken information
  • Understand instructions
  • Follow long conversations
  • Follow multi-step directions
  • Maintain focus on an activity if other sounds are present
  • Take written notes from speech
  • Complete verbal math problems
  • Learn songs or rhymes

Because these symptoms overlap with other disorders, auditory processing disorder cannot be diagnosed from this list of symptoms alone. The condition can only be diagnosed by audiologists, who use tests that measure specific auditory processing functions.

Symptoms like difficulty listening, remembering information, or understanding spoken language, make APD commonly confused with Attention Deficit Hyperactivity Disorder (ADHD) or dyslexia, but it is distinct from both.

With ADHD and dyslexia, there is no impairment of the processing of auditory input in the central nervous system.

Children with ADHD tend to exhibit inattention, distractibility, and hyperactivity in any environment, while children with APD usually don’t have difficulty focusing and paying attention in quiet environments.

While those with dyslexia also have difficulty memorizing, spelling, thinking and/or understanding, these difficulties do not exist because of an inability to hear clearly. Unlike APD, dyslexia is a language-based learning disability.

Sources: American Speech-Language-Hearing Association; Auditory Processing Center; Understood.org

BACK TO AUDITORY PROCESSING DISORDER OVERVIEW

Several populations show a high prevalence of APD:

  • In the U.S., it is estimated five percent of school-age children, or 2.5 million children, have APD. The true prevalence may be greater due to undiagnosed or misdiagnosed cases. At any level of education, untreated APD can impede academic progress.  
     
  • People with autistic spectrum disorder (ASD, or autism) often show difficulties with auditory processing. Autism is a developmental disability that can cause significant social, communication, and behavioral challenges. Processing auditory information is critical to social communication, and people with autism spectrum disorders typically have problems processing information received from verbal communication. APD is a common secondary diagnosis for children with autism.

    Studies have shown a strong link between Fragile X Syndrome (FXS), the most common genetic form of autism, and difficulties with sound localization. FXS is characterized by impaired cognition, hyperactivity, seizures, attention deficits, and hypersensitivity to sensory stimuli, specifically auditory stimuli.
     
  • An estimated 15% of military veterans live with APD due to blast exposure. HHF’s Emerging Research Grants recipient Edward Bartlett, Ph.D., explains that the changes to the central auditory system may account for the behavioral issues that veterans experience, such as problems with memory, learning, communication, and emotional regulation.
  • Older adults, including those with typical or near-typical hearing, may exhibit age-related central auditory processing deficits. Scientists have confirmed that changes in both the peripheral and central auditory systems occur as a result of aging. These changes can impact auditory and cognitive processing abilities that are important for speech understanding. Such individuals experience reduced speed of information (sensory and mental) processing, which, can affect listening comprehension. Speech understanding especially in adverse or challenging environments has been related to listeners' working memory capacity.

  • Individuals with neurological disorders as a result of brain injuries (i.e. stroke, traumatic brain injury, tumors, epilepsy) are more susceptible to APD because of damage to the central nervous system.


Sources: Auditory Processing Center; Autism Research Institute; Journal of Rehabilitation Research & Development; National Institute on Deafness and Other Communication DisordersSeminars in Hearing

There are no cures for APD, but there are many treatments that aim to improve the effectiveness of everyday communication. As it is a neurological problem, it cannot be treated with medication.

A successful treatment plan for APD incorporates many different approaches.

Environmental modifications: These modifications fall into two types, bottom-up and top-down, and aim to create a redundant listening and learning environment.

  • Bottom-up environmental modifications, which are acoustic-based, include: hearing assistive technology, architectural interventions to reduce reverberation, and preferential seating away from adverse noise.

  • Top-down environmental modifications, which change how information is imparted, include: checking for comprehension, complementing verbal speech with visual cues, slowing the speaking rate, repeating key information, providing written instructions, and providing a notetaker.

Speech-language pathology (speech therapy): Because children with APD struggle with sound discrimination—differentiating between similar sounds—speech-language pathologists (SLPs) can help them perceive these sounds better and more clearly. SLPs can also help children improve perception of individual sounds (phonemes) in words, which can help with reading, employ active listening skills, and use appropriate language in social situations.

Compensation strategies: Individuals with APD can be taught skills to compensate for weak listening ability. Examples include teaching the patient to be more proactive when in a learning environment, such as requesting clarification, asking a person to repeat directions, or using a recording device.

Auditory training: This intervention directly attempts to improve the function of the affected auditory process(es) by addressing auditory skills. Training can be formal or informal:

  • Formal auditory training uses recorded stimuli (e.g., tones, noise, speech, digits) presented via an audio device. The stimuli may be routed through an audiometer for control. Performance is scored periodically and training difficulty is modified to bring performance closer to the criterion.

  • Informal auditory training does not use stimulus control with an audiometer; instead they are presented face-to-face rather than played from a recording on a device.


Sources: American Speech-Language-Hearing Association; Child Mind Institute; Seminars in Hearing; Strickland Ear Clinic; Understood.org

Thanks to the generosity of Royal Arch Masons, Hearing Health Foundation (HHF) funds groundbreaking research to advance our scientific understanding of Auditory Processing Disorder (APD).

Grants focused on APD are awarded annually to promising scientific investigators through the Emerging Research Grants (ERG) program.
 

LATEST APD SCIENTIFIC PROJECTS FUNDED BY HHF'S EMERGING RESEARCH GRANTS

  • Joseph H. Bochner, Ph.D., Rochester Institute of Technology, is focused on understanding the impact of sensorineural (peripheral) hearing loss may extend to central auditory processing when the onset of hearing loss occurs at birth or within the first two to three years of life. 
     
  • Angelo Yarnell Bonino, Ph.D., CCC-A, University of Colorado Boulder, is researching toddlers’ and preschoolers’ auditory functioning with stimuli that are believed to be highly related to speech and language abilities.
     
  • Inyong Choi, Ph.D., University of Iowa, seeks to develop clinical tests to identify specific hearing deficits that are currently undiagnosed and raise awareness of such “hidden” hearing loss.
     
  • Christina Reuterskiöld, Ph.D., New York University, aims to better understand the implications of early auditory deprivation on auditory processing, language, and literacy learning in children, which will ultimately lead to improvements in targeted intervention and educational approaches for these children.
     
  • Richard A. Felix, II, Ph.D., Washington State University Vancouver, seeks to gain a thorough understanding of the neural mechanisms that govern the temporal processing of speech. This work has the potential to impact those with hearing loss by providing vital information needed for treatments designed to ameliorate listening problems associated with APD.
     
  • Elizabeth McCullagh, Ph.D., University of Colorado, is focused on how the auditory brainstem functions in autism in order to lead us to greater insights to the disorder in general, as well as specifically in auditory dysfunction, and ultimately to provide a medical intervention to restore the balance of excitation and inhibition in autistic patients.
     
  • Nathan Higgins, Ph.D., Vanderbilt University, seeks to establish consistent biomarkers for central auditory processing, and determine the utility of fNIRS for a variety of patient populations by quantifying the influence of task-related attention on cortical activity. This will aid the development of neuroimaging-based assessments of central auditory function that can then be used by clinicians to help diagnose and focus treatment for individuals with APD.
     
  • Nirmal Kumar Srinivasan, Ph.D., Towson University, aims to understand the difficulties encountered by listeners with APD in complex listening environment. Findings from this project will lead to a series of studies to identify relevant tests that would separate listeners with hearing loss and APD; identify test variables that captures most of the underlying variance in the difference in performance with aging and hearing loss; develop tests that could be used in clinical settings to quickly estimate the extent of processing deficits; and develop effective rehabilitation and intervention for listeners with APD.
     

RECENT APD DISCOVERIES BY HHF-FUNDED SCIENTISTS

  • Richard A. Felix, II, Ph.D., produced evidence that lower-level subcortical areas may play a significant role in hearing disorders. Subcortical pathways represent early-stage processing on which sound perception is built; therefore problems with understanding complex sounds such as speech often have neural correlates of dysfunction in the auditory brainstem, midbrain, and thalamus. Learn more. 
     
  • Yoojin Chung, Ph.D., looked at the neural mechanisms underlying the limitations of clinical bilateral CIs as they relate to understanding conversations in noise and suggested improvements, such as delivering ITD information in low-rate pulse trains. Learn more. 
     
  • Elizabeth McCullagh, Ph.D., performed the first study that explored alterations in glycinergic inhibition in the auditory brainstem of FXS mice. Given the findings in this study, further knowledge of the alterations in the lower auditory areas, such as the tonotopic differences in inhibition to the MNTB, may be necessary to better understand the altered sound processing found in those with FXS. Learn more. 
     
  • Andrew Dimitrijevic, Ph.D., was published for his study that measured alpha rhythms during attentive listening in a commonly used speech-in-noise task, known as digits-in-nose (DiN), to better understand the neural processes associated with speech hearing in noise. Dimitrijevic and his colleagues’ novel findings propel the field’s understanding of the neural activity related to speech-in-noise tasks. Learn more.