What is Auditory Processing?

Auditory processing has been defined as the "utilization of acoustic information by the auditory system” (Schoeny, cited in Musiek et al, 1990).  It has also been described as "the building that we do upon the auditory signal to make the information functionally useful…how we clarify, locate, alter, analyse, store and retrieve the information” (Katz & Wilde, cited in Katz, 1994).  More simply it has been referred to as "what we do with what we hear” (Katz & Wilde, cited in Katz, 1994).

Auditory processing is a complex phenomena encompassing a variety of auditory system mechanisms.  The American Speech-Language-Hearing Association (ASHA) Task Force on Auditory Processing (1996) referred to central auditory processes as the "auditory system mechanisms and processes responsible for the following behavioural phenomena.”  Further clarification of each behavioural phenomena (as indicated by the bracketed definitions) is provided by Matson (2005).

• Sound localization/lateralization (the ability to know where sound has occurred in space);
• Auditory discrimination (the ability to distinguish one sound from another);
• Auditory pattern recognition (the ability to determine similarities and differences in patterns of sounds);
• Temporal aspects of audition (abilities to sequence sounds, integrate a sequence of sounds into meaningful combinations, and perceive sounds as separate when they quickly follow one another);
• Auditory performance decrements with competing acoustic signals (ability to perceive speech or other sounds when another signal is present);
• Auditory performance decrements with degraded acoustic signals (ability to perceive a signal in which some of the information is missing).

A weakness in one or more of the above behaviours is considered to be an auditory processing disorder (APD) (ASHA, 1996).  APD has also been broadly interpreted as "a deficit in the processing of information that is specific to the auditory modality…(which) may be associated with difficulties in listening, speech understanding, language development and learning” (Jerger & Musiek, 2000).

Sound familiar?

Children with undetected auditory processing difficulties are often referred to in such ways.  These are the sorts of comments typically received from parents prior to the identification of an APD.  For some children who present for a hearing assessment, a hearing loss, and commonly a fluctuating hearing loss caused through middle ear complaints may partly or wholly account for the reported listening issues.  However when a hearing deficit has been successfully excluded, parents are often at a loss to explain the listening behaviour of their child.  The child appears to have problems with their listening, but the parent is being told that hearing levels are fine.  Although children with hearing loss can also have/are not exempt from auditory processing problems, most children who present for formal assessment of their auditory processing skills exhibit normal hearing thresholds and are of generally normal intelligence.  However these children experience mild to severe listening problems caused through weakness in the ability to successfully process auditory information, often having difficulties making sense of what they hear and frequently appearing as if they have a hearing impairment or an attentional problem. The role that audition plays in learning is significant, and this is especially so in the early childhood years when essential basic skills are being taught and a solid foundation for further learning is required.

When an APD exists, learning generally becomes more challenging and sometimes too difficult without special/additional assistance (Florida Department of Education, 2001).  Children in a classroom setting can spend a significant portion of the day engaged in listening-based tasks, highlighting the importance of the auditory modality in the learning process of the child.  Although an APD can and often does co-exist with a number of other disorders (for example, cognitive, language or attentional disorders), thorough assessment of auditory processing abilities and usually a team approach is required to enable specific differential diagnosis.  A comprehensive auditory processing evaluation which encompasses assessment of the several auditory behaviours classified under the umbrella of auditory processing should see as the result a pattern of findings which can facilitate this differential diagnosis.  For instance, the isolation of patterns consistent with APD can "assist in differentiating attention and auditory deficits…on behavioural and electrophysiological tests of central auditory function ADHD and (C)APD result in different findings" (Bellis, 2003).  It is the concept of result patterns and their interpretation that is essential in contributing to the process of differential diagnosis, and in understanding that "(C)APD is a heterogenous disorder that yields specific patterns of test findings of behavioural central auditory tests" (Bellis, 2003).

What are the characteristics of APD?

Characteristics common in children with diagnosed APD include the following:

• Frequent requests for verbal information to be repeated – often saying "Pardon?" or "What?"
• Slow or delayed responses to verbal requests/instructions
• Difficulty following verbal instructions/often misunderstanding what has been said
• Difficulty hearing in background noise
• Distractibility/"tunes out"/short attention span
• Difficulties with reading/spelling/reading comprehension
• Problems with phonic analysis
• Problems understanding rapid/degraded speech
• A dislike of/sensitivity to loud sounds/noise
• Behavioural concerns – aggressive/withdrawn/impulsive
• Problems with recall/re-telling stories
• Poor listening skills
• Behaves as if a hearing loss is present, despite normal hearing
• Confusing similarly sounding words
• Reversals in reading and writing
• Receptive and/or expressive language problems
• Appearing to tire/fatigue easily when engaged in listening tasks/with complex auditory stimuli.
• Confusion with sound localization
• Following other children/looking for visual cues from other children before commencing work
• Motor skills (gross and fine) may be deficient
• Verbal IQ scores often lower than performance scores
• May refuse to participate in class discussions or respond inappropriately
• Difficulty completing assigned tasks.

As a number of these behavioural characteristics can and are often shared by other disorders, and therefore may be manifested by other causative factors or indeed exacerbated by hearing and/or auditory processing issues, comprehensive auditory assessment and the results from multidisciplinary assessments enable focusing on the whole child and help to determine the potential impact/significance of APD results and the directions to be taken regarding appropriate management.

What are the causes of auditory processing disorders?

Auditory processing difficulties can be present in both children and adults.  In the paediatric population specifically, the research refers to several underlying mechanisms for central auditory disorders.  The main influences include:

• Maturational delay of the Central Auditory Nervous System (CANS) (Musiek et al, 1990).
• Developmental abnormalities (inappropriate development of the auditory/language areas of the brain) (Musiek et al, 1990).
• Neurologic disease/insult/injury (seizure activity/head trauma) (Musiek et al, 1990).
• An early and frequent history of otitis media during the critical period for speech-language development.  Research suggests that prolonged otitis media with static or fluctuating hearing loss can lead to central auditory processing deficits that can cause language and learning delays long after the middle ear problem is treated (Keith, cited in Matson, 2005).

Research has also outlined other potential influences:

• Genetic links (Katz & Wilde, cited in Katz, 1994).
• Gender differences (APD more prevalent in males) (Katz & Wilde, cited in Katz, 1994).

Many children with APD will "grow out" of the problem, with research indicating this to be the case with approximately 60% of children (Centre for Auditory Research, 1997).  However this figure also highlights a significant number of children who may still possess APD in later years, and further emphasizes the importance of identification and the co-ordination of appropriate management to minimize the effects of the disorder on learning and other possible areas (for example, emotional and social functioning).

What is the prevalence of central auditory processing disorders?

Research estimates have offered a prevalence of 2-3% in the paediatric population (Chermak and Musiek, cited in Florida Department of Education, 2001), with other estimates being as high as 3-5% (Santucci, cited in Matson, 2005).  The literature also indicates a 2:1 ratio of boys to girls (Chermak and Musiek, cited in Florida Department of Education, 2001).  In addressing the prevalence of APD in the adult population, a research study by Cooper and Gates (1991) estimated an APD  prevalence rate of 23% in those over 63 years of age.  Stach et al (cited in Matson, 2005) outlined that "Reports of prevalence of APD in the older adult population vary, ranging from well over 50% in clinical studies."

What are some of the consequences of APD?

Children with APD often under-achieve, performing below their true potentials in the learning setting (Centre for Auditory Research, 1997).  The impact of severe auditory processing deficits are often far-reaching and dramatic, affecting learning, language, socialization and general life skills (Bellis, 2002).  APD in the early school years can interfere with the acquisition of basic skills, thereby making it more difficult to build a solid foundation onto which further learning demands can be adequately consolidated.  The early identification of APD allows many of the learning and social problems that can accompany it to be addressed and treated (Bellis, 2003).  This is especially important as it helps the child’s confidence to be protected as his/her specific learning needs are better accommodated and the approach/es implemented that will best complement the child’s strengths.

What is involved in an auditory processing assessment?

A full assessment of hearing is of utmost importance prior to an evaluation of auditory processing ability.  Taking into account that a child with a hearing loss, including those with a slight hearing deficit, can demonstrate characteristics quite similar to those children with identified auditory processing problems, reinforces the need for a comprehensive assessment of hearing sensitivity before any assessment of central auditory functioning is undertaken.  As discussed earlier, it is also possible for individuals with a hearing loss to have both a hearing deficit and specific weaknesses in auditory processing.  Although certain tests of auditory processing may not be available to individuals with a hearing loss, there are some tests which can be administered once an idea of hearing sensitivity level and discrimination capacity become evident.  In those cases the dual issues of both hearing deficit and APD can be addressed.

A full hearing evaluation at the Lions Hearing Clinics involves taking a detailed history so that information relating to ear health, a possible family history of hearing loss, academic concerns and possible attentions/behavioural issues can be recorded and the main focus for the assessment determined.  It is also important at this time to share outcomes from other assessments the child may have had, such as a paediatric assessment and/or speech-language evaluation, in order to gain an understanding of existing areas of strengths and weaknesses which will enable a more "wholistic" interpretation of results and help determine the type of recommendations needed for a particular case.  An assessment of middle ear function (tympanometry) is then undertaken to help identify a potential disorder affecting the middle ear system which may require treatment, a common dysfunction of the middle ear in children being otitis media (defined as an inflammation of the middle ear).  An evaluation of hearing is subsequently co-ordinated to assess sensitivity across a range of frequencies to determine whether the child would be expected to adequately hear and be able to receive all the intricacies of speech. This is followed by speech audiometry assessments to investigate the child’s discrimination ability for speech.  Once these measures have been established a decision is then made regarding the appropriateness of pursuing the auditory processing part of the evaluation. A significant middle ear condition such as "glue ear" for example, would first require medical treatment, the child then returning to the clinic for formal assessment of auditory processing ability following resolution of the condition.
If the decision is made to proceed with the full auditory processing evaluation, the child is required to sit through an assessment ranging from 45 minutes to one hour, depending on age level and specific requirements.  Results of the assessment are then thoroughly discussed with parents and a detailed report issued.  Please note:  [All hearing and auditory processing tests at the Lions Hearing Clinics are carried out in strictly controlled conditions (in a sound proof room) using regularly monitored and calibrated testing equipment for exact presentation of desired stimuli levels.  Such testing conditions are critical, particularly when undertaking speech-in-noise and other processing test types].

A broad range of auditory processing tests are used at the Lions Hearing Clinics to allow the skill evaluation of children from generally five years of age through to adults.  Central auditory processing test batteries employed at the clinics are comprised of a variety of behavioural measures of central auditory function in order to provide comprehensive assessment of the auditory behaviours listed earlier.  These tests are not intrusive and require the child to listen via headphones and to respond accordingly.  In addition to several other sub-tests, the assessments of speech-in-noise ability and Short-Term Auditory Memory (STAM) are routinely included in our paediatric auditory processing test batteries.

A comprehensive assessment of hearing and central auditory processing skills should be undertaken by experienced audiologists.  At the Lions Hearing Clinics, all auditory processing assessments are provided by fully qualified, university-trained, experienced audiologists with backgrounds which include education and psychology.  The implementation of full hearing and auditory processing evaluations by an audiologist is especially important considering the potential need for medical referrals and further investigation in some cases, this based on the pattern of results obtained on either or both the hearing and auditory processing evaluations.  In a small number of cases, referral to a medical specialist may be required to exclude possible neurological conditions influencing learning difficulties in some children.

What can be done to help a child with APD?

In recent years a number of management approaches have emerged in the area of central auditory processing.  Considered to be essential in the management of many children with auditory processing weakness is the implementation of environmental modifications and classroom-based teaching suggestions/strategies.  The main aim of such management is to enhance the child’s access to auditory information in their learning environment/s so that coping abilities can be further promoted and learning heightened. A variety of strategies can be recommended, depending on the specific processing deficits identified from the processing evaluation. Providing a preferential seating position for example, and strategies to help minimize background noise level, in addition to other practical management suggestions, would be considered important for the child who performs poorly in the speech-in-noise sub-test during the auditory processing evaluation. In some cases a trial of a Frequency Modulated (FM) amplification unit may also be considered part of the desired management programme for a specific child, although the device may not always be deemed suitable. The utilisation of more visual cues in the learning process is appropriate for many children with auditory processing weaknesses, although depending on the auditory processing profile determined from the full processing assessment, the addition of visual or multimodality cues may have restricted benefit in some cases (Bellis, 2003).  Specific strategies for teachers to employ in the learning setting of children with CAPD include attracting and securing the child’s attention prior to be spoken to and  undertaking regular check’s on the child’s comprehension of verbal instruction. Other strategies for teachers to incorporate in their classrooms for children with CAPD are also discussed with parents and listed in a report, the type of strategies recommended for students again being influenced by the CAPD profile type to have emerged following the full auditory processing assessment.

Relaying several principles of active rather than passive listening is also an important part of follow-up for children with CAPD.  Compensatory skills such as "whole-body" listening techniques and encouraging children, especially older children to analyze their listening and learning environments and to be aware of problem-solving strategies to facilitate better overall listening, are generally considered essential parts of the auditory processing management process (Bellis, 2003).  However, as outlined earlier, certain active listening techniques which may be appropriate for most children with CAPD, may not be wholly effective with others, and recommendations should be made taking into account the auditory processing profile developed as a result of the full processing assessment and the child’s specific difficulties.

Deficit-specific training is another area attracting further interest in the management of auditory processing in more recent times. Although there is somewhat limited documented evidence to date on the efficacy of deficit-specific/remediation strategies to facilitate development of a weaker area of auditory processing, knowledge of neuroplasticity has suggested that "increased stimulation" may…result in structural changes and functional improvement... So it may be with structures within the brain" (Bellis, 2003). Research continues to evolve in this area. In recent years, computer-based literacy therapy and auditory stimulation programs have also experienced increased public awareness as potential forms of additional intervention for children with CAPD. Parents can discuss with their audiologist whether trial of such programs would be considered appropriate for their child, based on results outcomes and the specific individual needs of the child. Research into the efficacy of these programs also continues to be undertaken.

Depending on the pattern of results from the auditory processing assessment and the individual difficulties, behaviours and needs of a particular child, further assessment and subsequent input/therapy from other important specialists including speech-language pathologists, occupational therapists, educational psychologists and paediatricians may also be required.

It should be acknowledged that not all children learn in the same manner. We all have strengths and weaknesses, and it is our weaker areas that can have the greatest impact on learning. A thorough assessment of hearing and auditory processing skills can help isolate if weaknesses exist in the auditory modality which may be having a negative impact on learning progress and attainment. The Lions Hearing Clinics should be contacted if further information on auditory processing or an appointment time for your child is required.

References

American Speech-Language-Hearing Association (ASHA), (1996), Central auditory processing:  Current status of research and implications for clinical practice.  ASHA Task force on central auditory processing consensus development.  American Journal of Audiology, vol 5 (2), pp41-54.

Bellis, T.J., (2002). When the Brain Can’t Hear: Unravelling the Mystery of Auditory Processing Disorder, Atria Books, New York.

Bellis, T.J., (2003).  Assessment and Management of Central Auditory Processing Disorders in the Educational Setting:  from Science to Practice, (2nd ed), Delmar Learning, New York.

Centre for Central Auditory Research, (1997). Central auditory processing disorder, Department of Electrical and Computer Engineering, Colorado State University,  Colorado.

Cooper, J.C., and Gates, G.A., (1991),  Hearing in the elderly – The Framingham cohort, 1983-1985:  Part II.  Prevalence of central auditory processing disorders.  Ear and Hearing, vol 12 (5), pp304-311.

Florida Department of Education, (2001).  Technical assistance paper (10967):   Auditory processing disorders, Bureau of Instructional Support and Community Services, Florida.

Jerger, J. and Musiek, F. (2000).  Report of the consensus conference on the diagnosis of auditory processing disorders in school-aged children. Journal of the American Academy of Audiology, vol 11 (9), pp467-474.

Katz, J and Wilde, L., 1994, Auditory Processing Disorders, In: Katz, J, (ed). Handbook of Clinical Audiology, Williams and Wilkins, Baltimore.

Matson, (2005) Central auditory processing: A current literature review (Part I),  (http://dspace.wustl.edu/bitstream/1838/13//Matson.pdf).

Musiek, F.E., Gollegly, K.M., Lamb, L.E. and Lamb, P., (1990). Selected issues in screening for central auditory processing dysfunction. Seminars in Hearing. 11 (4), 372-384.