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LANGUAGE , S PEECH , AND H EARING S ERVICES IN S CHOOLS • Vol. 30 • 339–344 • October 1999 © American Speech-Language-Heari ng Association 3390161–1461/99/3004–0339

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LSHSS

Clinical Forum

Treatment for Central Auditory Processing Disorders

Clinical Issues in Central AuditoryProcessing Disorders

Robert W. KeithUniversity of Cincinnati, OH

ver the years, a substantial amount of research has been published indicating thatcertain children, adolescents, and adults with

ABSTRACT: Speech-language pathologists are often facedwith the need to assess and treat the suspected auditoryprocessing problems of children with language andlearning difficulties. This article discusses central auditoryprocessing disorders (CAPDs). Included are a discussion of background information, a current definition of CAPDs, ageneral discussion of test battery approaches following

suggestions made by the American Speech-Language-Hearing Association (ASHA) Task Force on CentralAuditory Processing Consensus Development (1996), andvarious approaches to intervention with persons identifiedas having a CAPD. Finally, there is brief discussion of remaining questions to be answered. The article attemptsto examine various controversies related to all aspects of CAPDs and increase the reader’s awareness of currentissues concerning this disorder.

KEY WORDS: central auditory processing disorders,central auditory processes, sensitized speech tests,remediation, language disorders

normal hearing have difficulty understanding speech andlanguage through the auditory modality. These individualshave difficulties with all types of acoustic distortions of auditory information including, for example, reverberation,background noise, acoustic filtering, rapid speech, andcompeting speech. In fact, the basic difficulty with anauditory processing disorder is that any speech signalpresented under less than optimal conditions is difficult tounderstand. The type of distortion is irrelevant to the main

problem of a disturbance in auditory processing. Theseindividuals have become known as persons with centralauditory processing disorders (CAPDs).

The term “central” emerged years ago, and was originallymeant to differentiate between the diagnosis of auditoryprocessing disorders that occurred at brain stem and corticallevels (i.e., the central auditory nervous system) from thoseoriginating in the cochlea or auditory nerve (i.e., theperipheral auditory system). An example of distortionoccurring in the cochlea is auditory recruitment resultingfrom endolymphatic hydrops. An example of distortionoccurring in the auditory nerve is auditory fatigue associatedwith an acoustic tumor. Both result in reduced speechdiscrimination. Other terms used in the past to describeCAPDs include central deafness, auditory agnosia, dysacusis,central auditory imperception, auditory processing disorders,central hearing loss, non-sensory hearing loss, and obscureauditory dysfunction. Whatever the label, what is common tothis population is that they have normal or near-normalhearing but have difficulty understanding speech under less

than optimal listening conditions. It may be unfortunate thatthe word “central” became associated with auditory process-ing disorders because that term does not appear to clarify theproblem and is a continuing source of controversy andmisunderstanding.

Professionals interested in communication disorders haveworked to understand CAPD and its possible relationship tolanguage, reading, and learning problems. The problem of understanding this disorder becomes more complex whenother difficulties, such as attention deficit disorder (ADD),low intelligence levels, language delays, learning disabili-ties, and reading disorders, are present. When auditory,language, and learning problems coexist, it is difficult to

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340 L ANGUAGE , S PEECH , AND H EARING SERVICES IN SCHOOLS • Vol. 30 • 339–344 • October 1999

determine which condition is primary and which is second-ary, or which causes the other to occur. For example, doesa CAPD “cause” a language/learning disorder? Are ADDand CAPD really the “same thing?”

Some professionals question the existence of CAPD as adistinct entity. However, most professionals in the field of communication disorders have encountered individuals who

have normal hearing, normal receptive and expressivelanguage, and normal attention, but have difficulty process-ing acoustically distorted speech, competing speech, orspeech in the presence of background noise. What is clear,therefore, from a clinical (some would say anecdotal)perspective, is that CAPDs do exist, independent of allother factors. Unfortunately, anecdotal evidence is not goodscience, and it is necessary to be more rigorous in develop-ing an understanding of this particular auditory disorder.

DEFINITION OF A CAPD

Various committees of the American Speech-Language-Hearing Association (ASHA) have attempted to developcoherent statements of understanding concerning CAPDs.The most recent attempt was the ASHA Task Force onCentral Auditory Processing Consensus Development (1996)(referred to as the Task Force). This report is necessaryreading for anyone who is seriously interested in thisdisorder. The Task Force included speech scientists, speech-language pathologists, and audiologists.

The definition of a CAPD advanced by the Task Force isbased on the principle that central auditory processes are theauditory system mechanisms and processes responsible for thefollowing behavioral phenomena. These processes include:

• sound localization and lateralization;

• auditory discrimination;

• auditory pattern recognition;

• temporal aspects of audition, including:

• temporal resolut ion,

• temporal masking ,

• temporal integrat ion, and

• temporal ordering ;

• auditory performance decrements with competingacoustic signals; and

• auditory performance decrements with degradedacoustic signals.

The definition of a CAPD proposed by the Task Force is“an observed deficiency in one or more of a group of mechanisms and processes related to a variety of auditorybehaviors” (ASHA Task Force on Central Auditory Process-ing Consensus Development, 1996, p. 43). This definition of a CAPD is inclusive, recognizing the contribution of neurocognitive, attentional, and auditory factors. Thedefinition applies to nonverbal, as well as verbal, signals andis broader than the construct of CAPDs proposed by Cacaceand McFarland (1998), which includes only non-linguisticfactors. Their exclusive definition limits the approach to

assessment and remediation that professionals would take.Therefore, although general agreement exists that CAPDsexist, there is not consensus on where to “draw the line” forspecifics of the definition. This lack of consensus is still along way from the position taken by Rees (1973) manyyears ago, who found evidence for CAPDs so limited thatshe gave up the search as being “futile.”

WHO SHOULD BE TESTED FOR A CAPD?

There are least two approaches for identifying childrenwho should be tested for the possible presence of a CAPD.They include: (a) identifying children who fall in certaincategories on various checklists of auditory performance(e.g., Sanger, Freed, & Decker, 1985; Smoski, Brunt, &Tannahill, 1992), and (b) referral on the basis of certainobserved behaviors. Children with a CAPD may exhibitsome of the following 10 characteristics (Keith, 1999):

• Normal pure-tone hearing thresholds: Some have asignificant history of chronic otitis media that hasbeen treated or resolved.

• Inconsistent responses to auditory stimuli: Childrenoften respond inappropriately, but, at other times, theyseem unable to follow auditory instructions.

• Difficulty with auditory localization skills: This mayinclude problems with telling how close or far awaythe source of the sound is and differentiating soft andloud sounds. Also, there are frequent clinical reportsthat these children become frightened and upset whenthey are exposed to loud noise, and often hold theirhands over their ears to stop the sound.

• Difficulty with auditory discrimination.

• Deficiencies in remembering phonemes and manipulat-ing them: These difficulties may be evident on taskssuch as reading, spelling, and phonics, as well asphonemic synthesis or analysis (Katz, 1992, p. 84).

• Difficulty understanding speech in the presence of background noise.

• Difficulty with auditory memory, either span orsequence, and poor ability to remember auditoryinformation or follow multiple instructions.

• Poor listening skills: This problem may be character-ized by decreased attention to auditory information,distractibility, or restlessness in listening situations.

• Difficulty understanding rapid speech or persons withan unfamiliar dialect.

• Frequent requests for information to be repeated. Forexample, one teacher described these children assaying “huh” and “what” frequently.

The profiles of these children often include significantreading problems, poor spelling, and poor handwriting.They may have articulation or language disorders. In theclassroom, they may act out frustrations that result fromtheir perceptual deficits, or they may be shy and withdrawnbecause of the poor self-concept that results from multiple


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Keith: Clinical Issues 341

failures. Children who exhibit these behaviors are candi-dates for central auditory testing (Keith, 1999).

The Test Battery Approach

A number of test procedures have been suggested toassess children, adolescents, and adults who have com-plaints of difficulty understanding speech in non-optimalacoustic conditions. In fact, specific tests have not changedmuch over the years since the early investigation of sensitized speech (Calearo & Antonelli, 1973). At that time,sophisticated radiologic imaging procedures were unavail-able, and the purpose of central auditory testing was toidentify brain lesions in adult subjects. That purpose isvery different from today’s purpose, where central auditorytesting is used to identify auditory processing disorders inchildren and adults with language and learning problems.Bergman, Hirsch, Solzi, and Mankowitz (1987) called thepurpose of CAPD testing the identification of “functionaldisorders of auditory communication” (p. 147).

The test battery that follows from the Task Forcedefinition of CAPD attempts to examine the mechanismsand processes thought to be responsible for certain auditorybehaviors. The components of the assessment recommendedby the Task Force include:

• history;

• observation of auditory behaviors;

• audiologic test procedures;

• pure tones, speech recognition, immittance;

• temporal processes;

• localization and lateralization;

• low redundancy monaural speech;• dichotic stimuli;

• binaural interaction procedures; and

• administration of speech-language measures.

The Task Force recognized that middle, late, and event-related evoked potentials are still being developed but canalso be used in the assessment of CAPDs. Use of event-related evoked potentials seems warranted based on someevidence that electrophysiologic findings are abnormal inchildren with receptive and expressive language disordersand CAPDs (Diniz, Albernaz, Munhoz, & Fukuda, 1997;Jirsa & Clontz, 1990; Kraus et al., 1993).

Specific Test Procedures

In regard to audiologic test procedures, low redundancyspeech refers to such tests as filtered words and auditoryfigure-ground (speech-in-noise) testing. Monaural testing isconducted using earphones, with the signal heard in one earat a time. Dichotic testing is conducted by presentingdifferent acoustic stimuli with simultaneous onset and offsettimes by earphone to the two ears. Dichotic stimuli includeconsonant-vowel syllables, digits, monosyllable words, twosyllable words (spondees), and sentences. Binaural interac-tion procedures are conducted by presenting different

stimuli simultaneously to the two ears, with interactionbetween the stimuli resulting in comprehension of acomplete message (e.g., binaural fusion tests), or compre-hension depending on changes in masking conditions (e.g.,Masking Level Difference Test). Readers will note the Task Force suggestion that a speech-language evaluation beconducted in concert with the inclusive definition of

CAPDs. The Task Force was not specific in recommendingspecific auditory or speech and language tests.

There are many excellent sources of information on testsof central auditory function including, but not limited to,textbooks by Pinheiro and Musiek (1985), Katz, Stecker, andHenderson (1992), Katz (1994), Roeser and Downs (1995),Bellis (1996), and Hall and Mueller (1997). Readersinterested in details of the administration and interpretationof central auditory tests are directed to these resources.

Suggested Parameters for Evaluating CentralAuditory Tests

When selecting a central auditory test battery, theexaminer should consider a number of factors. Theseinclude the purposes of the test, its modality, normativedata, efficiency, validity, and reliability. Important factorsto consider are: (a) whether the test is single modality(auditory) or cross-modality (auditory to visual), (b) thecontent of the signal (non-linguistic, low-linguistic, or highlinguistic content), and (c) the child’s age, intelligence, andability to respond appropriately to the test. The test chosenshould meet criteria for the following psychometric factors:validity (including content, construct, and criterion related)and reliability (including test-retest, inter-examiner, inter-item, and inter-form). Also, the examiner should evaluate

whether complete normative data are available and howthey were collected (Fallis & Keith, 1997).

TREATMENT APPROACHES TO PERSONSWITH A CAPD

There is little agreement concerning treatment approachesthat follow from the identification of a CAPD and even lessdocumentation of treatment outcomes. Two treatment terms(sometimes used interchangeably) are remediation andmanagement. However, these two terms have distinctmeanings. To remediate is to alter central auditory nervous

system function. Management, on the other hand, involvesmodifying behavior, performance, or environment withcompensatory or cognitive techniques (Keith & Fallis, 1998).Briefly, basic management strategies include: (a) modifica-tion of the environment, (b) perceptual training, (c) compen-satory training, and (d) cognitive training.

Recommendations for environmental modification mayinclude the use of a personal assistive listening device(ALD) or FM (frequency modulated) unit, preferentialseating, and classroom amplification (sound field) devices.The identified child may also be assigned a “listeningbuddy” to provide peer support for checking verbaldirections and assignments. Several authors (ASHA, 1991;


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DiSogra, 1995; Flexer, 1989, 1990; Scharff, Ray, &Bagwell, 1981) describe management strategies for theclassroom or home that are related to alterations of thephysical (or psychological) environment.

Recent studies on the benefits of perceptual trainingwere published by Merzenich et al. (1996) and Tallal et al.(1996). These authors described the positive effects of

computer-based games (known as Fast ForWord®

) that trainor modify temporal processing deficits in these children.Merzenich et al. claimed that “these studies stronglyindicate that the fundamental temporal processing deficitsof LLI children can be overcome by training” (p. 80). (Forfurther discussion of Fast ForWord ®, see the companionarticles by Veale and Gillam, this issue.)

Compensatory training, or auditory skills development,has been used to strengthen perceptual processes and teachspecific academic skills. There are many different ap-proaches to teaching auditory skills that presume to assistthe child with a CAPD. Some of these techniques include:

• speech sound discrimination (auditory discrimination)

(Sloan, 1986),• auditory analysis (Rosner, 1993),

• phonemic synthesis (auditory synthesis) (Katz, 1983),

• auditory memory strategies (Butler, 1983),

• auditory figure-ground training (Gillet, 1993),

• prosody training (Chermak & Musiek, 1997; Hargrove& McGarr, 1994; Hargrove, Roetzer, & Hoodin,1989), and

• temporal processing strategies (McCroskey, 1984;Tallal et al., 1996).

Cognitive training involves teaching the child to actively

monitor and self-regulate message comprehension skills anddevelop new problem-solving skills. Cognitive therapy mayinclude language training (linguistic or metalinguistic),vocabulary development, and the teaching of organizationalskills. In a discussion of metalinguistic strategies, Chermak and Musiek (1997) included “discourse cohesion, schemainduction, context-derived vocabulary building, segmenta-tion, prosody, and metamemory” (p. 192). Butler (1983)reported on the teaching of mnemonic strategies to assistthe child with a CAPD. She suggested using rehearsal,paragraphing, imagery, networking (building bridges tostore new concepts), analysis of new ideas, and key ideasto think systematically. Finally, cognitive therapy may alsoinclude the teaching of organizational skills, includingteaching the child how to:

• follow directions,

• use written notes,

• develop self-monitoring strategies,

• know what they know,

• listen and anticipate,

• ask relevant questions, and

• answer questions.

A number of texts and articles provide suggestions forthe management and remediation of children with CAPDs.

They include texts referenced previously, and a recent textby Masters, Stecker, and Katz (1998). Another resource forthe management or remediation of auditory skills may befound in Kelly (1995). There is a great need for outcomestudies that document the effectiveness of all of thetreatment suggestions listed here. While awaiting thesestudies, however, clinical experience indicates that children

with CAPDs are substantially helped using some of thetechniques discussed.

REMAINING QUESTIONS TO BEANSWERED

Speech-language pathologists will recognize that it takesyears to resolve questions regarding any clinical andresearch area. When this author entered the field of communication disorders, stuttering was little understoodand the subject of intense investigation. There were honestphilosophical differences and stirring debates betweenapproaches taken, for example, by Wendall Johnson at theUniversity of Iowa and Bryng Bryngelson at the Universityof Minnesota. Treatment modalities actually used in theclinic included forcing left-handed people to attempt tochange dominance by immobilizing their left hand anddoing such exercises as practicing table tennis with theright hand. Clearly the problem of stuttering is much betterunderstood and treated in 1999.

Further, as an audiologist, this author understands thatdisagreement exists among speech-language pathologistsconcerning the optimal method of obtaining languagesamples. Some individuals have the opinion that to obtain atrue picture of a child’s language development, it isnecessary to observe that child in a natural context andobtain language samples with different communicationpartners. Other individuals feel that standardized languagetesting, using a broad spectrum of diagnostic assessments,obtains an adequate picture of the child’s language abilities.

These examples are given only to point out, by analogy,that similar controversy exists in the area of CAPDs. Thereis general consensus that CAPDs exist, but consensus onthe approach to the assessment and remediation of childrenwith these disorders has not been reached. I suspect thatthere will never be a unitary approach either to assessmentor remediation because CAPD is a complex multifactorialdisorder. Just as with language disorders, each child

requires a slightly different approach to assessment andremediation because each child is different. There willprobably be better models of remediation developed in thefuture, and techniques for computer-assisted remediation,still in their infancy, will improve. Until we have bettermodels for remediation, many of the guidelines suggestedhere, and others not discussed, have helped some childrenwith CAPDs.

Many needs exist for the future. One need is to clarifydefinitions of CAPD and criteria used to diagnose personswith that disorder. In her companion article, Friel-Patti (thisissue) notes that CAPD is not one of the diagnosticcategories contained in the Diagnost ic and Stat ist ical


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Keith: Clinical Issues 343

Manual of Mental Disorders (American Psychiatric Associa-tion, 1994). In a recent book (Keith, 1999), this authoraddressed the need for mutually exclusive and exhaustivediagnostic criteria that would allow clinicians to diagnose,treat, and communicate about individuals with CAPD. Thereneeds to be clearer understanding of CAPDs and theirrelationship to language, learning, and ADD. Additional

normative data for available tests of central auditory functionare necessary, as is the development of new tests. We needto better understand how to relate central auditory testresults to specific treatment plans, and, most importantly ,there needs to be a better understanding of treatments thatwork best for children and outcome studies to verify theireffectiveness. We have traveled a long distance, but we havea way to go before CAPD is completely understood.

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Received February 9, 1999Accepted June 30, 1999

Contact author: Robert W. Keith, Mail Location 670528,University of Cincinnati Medical Center, Cincinnati, OH 45267.Email: [email protected]

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