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Current Opinion in Neurology:
doi: 10.1097/WCO.0b013e328326f6b1
Developmental disorders: Edited by Bruce Shapiro

Auditory processing disorders: can they be treated?

McArthur, Genevieve M

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Macquarie Centre for Cognitive Science, Macquarie University, Macquarie, Australia

Correspondence to Dr Genevieve McArthur, Macquarie Centre for Cognitive Science, Macquarie University, NSW 2109, Australia Tel: +61 2 985 0 9162; e-mail: genevieve.mcarthur@maccs.mq.edu.au

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Abstract

Purpose of review: In recent years, parents and schools have spent millions of pounds and dollars on commercial programs that claim to treat children's developmental disorders by training their auditory processing. Here I test the truth of this claim using evidence from recent auditory training studies done with children with developmental disorders.

Recent findings: Six studies were published in 2007 and 2008 that trained children with developmental disorders on an auditory training program that included nonspeech sounds or simple speech sounds. The results suggest that nonspeech training and simple speech training can treat children's auditory processing disorders. However, this training has little or no effect on their reading, spoken language, or attention.

Summary: This conclusion suggests that commercial training programs could increase their efficiency (and decrease their cost) by removing redundant nonspeech and simple speech training components. The dearth of well controlled auditory training studies, paired with the misleading nature of poorly controlled studies, suggests that we need to teach parents, teachers, and the media how to separate the good training studies from the bad ones.

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Introduction

A child is said to have an auditory processing disorder (APD) if she or he scores poorly on a test that asks them to detect, identify, discriminate, order, group, or localize sounds. An APD is thought to affect the processing of both nonspeech and speech sounds. However, the best tests for APDs use nonspeech sounds because nonauditory factors, like language exposure or language expertise, can confound responses to speech sounds [1••].

Can a child's APD be treated? To answer this question, I will first discuss who has an APD, how APD is treated, and how APD treatments should be tested. I will then use the results of the most recent auditory training studies done with children with developmental disorders to conclude if APD treatments improve APDs or the symptoms of developmental disorders. Finally, I will outline the practical implications of this conclusion.

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Who has an auditory processing disorder?

In the last 40 years, over 75 studies have found that children with specific reading disability (SRD; also known as developmental dyslexia) or children with specific language impairment (SLI) perform poorly on nonspeech auditory tests [2]. These results are supported by many brain studies finding that children with SRD or SLI have atypical brain responses to nonspeech sounds [3]. A smaller number of studies have found that children with attention deficit hyperactivity disorder (ADHD) and children with autism (i.e. autistic spectrum disorder) also have an APD [4,5]. So APDs seem to be associated with SRD, SLI, ADHD, and autism.

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What about ‘central auditory processing disorder’?

Central auditory processing disorder (CAPD) is an unofficial diagnosis that is nevertheless becoming popular in the UK, US, Australia, and New Zealand. CAPD is also called APD. The confusion between this use of the term APD and my use of the term APD raises an important point. Some people use the terms CAPD and APD to refer to a diagnostic category. Other people use the terms CAPD and APD to refer to a type of processing problem. In this article, I use the term CAPD to refer to a diagnostic category and the term APD to refer to a type of processing problem.

To provide a clear description of CAPD is difficult: There is no consensus about the criteria or the types of tests that should be used to diagnose CAPD. It is also difficult to explain why a diagnosis of CAPD is clinically useful: While many studies show that APDs are associated with SRD, SLI, ADHD, and autism, very few (if any) studies have proven that APDs actually cause these developmental disorders. The unknown quality of CAPD and causal effects of APD make it tempting to reject CAPD as a diagnostic category. However, it may prove wiser to heed the advice of Dawes and Bishop [1••]: ‘rather than abandoning the [CAPD] construct, we need to develop improved methods for assessment and diagnosis, with a focus on interdisciplinary evaluation’ (p. 3). Until this work is done, CAPD is too ambiguous to include in a list of developmental disorders associated with an APD.

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How is an auditory processing disorder treated?

Tables 1–4 summarize studies published in 2007 and 2008 that trained children with SLI, SRD, or autism on an auditory training program that included nonspeech sounds or simple speech sounds. These studies are organized according to the types of sounds included in the auditory training program:

Table 1
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Table 2
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Table 3
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Table 4
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1. Nonspeech studies: presented nonspeech sounds that differed in frequency [6••].

2. Simple speech studies: presented vowels and consonant–vowels (CVs) [6••].

3. Fast ForWord Language studies (FFW-L; Scientific Learning Corporation, Inc., Berkeley, California, USA): presented nonspeech sounds, simple speech sounds, and complex speech stimuli (syllables, words, and sentences) [7••–10••].

4. Tomatis therapy (TT) studies: presented frequency-filtered music and speech [11•].

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How should an auditory training program be tested?

A good study of an auditory training program has the following features:

1. It tests if trainees have an APD prior to training (see studies in the tables that have an auditory test listed in column 7 with a corresponding ‘y’ in column 8).

2. It tests if trainees have significantly better auditory processing after training (see studies with an auditory test in column 7 and a corresponding ‘y’ in column 9).

3. It tests if trainees have symptoms of SLI, SRD, ADHD, and autism before training (see studies with reading, spoken language or reading tests listed in column 7 that have a corresponding ‘y’ in column 8).

4. It tests if trainees' symptoms are significantly better after training (see studies with reading, spoken language or reading tests listed in column 7 that have a corresponding ‘y’ in column 9).

5. It tests a second group of children – who do no training – on the same pretraining and posttraining tests to gauge the effects of repeated testing and maturation on the measures (see studies with data in column 6 that have pretraining and posttraining data in columns 12 and 13).

6. A particularly good study will also test a third group of children – who do an unrelated type of training (e.g. maths training) – on the same pretraining and posttraining tests to detect any placebo effects on the measures (see studies with data in columns 4 and 5 that have pretraining and posttraining data in columns 10 and 11).

Of the six auditory training studies published in 2007 and 2008, only two included features 1–5 [6••,7••]. One study included features 2–5 [9••]; one study included features 3–6 [8••]; one study included features 2–4, and 6 [10••]; and the last study only included features 4 and 6 [11•].

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Which auditory training programs treat auditory processing disorder?

The information in columns 7–13 of Tables 1–4 can be used to ascertain which auditory training programs treat APD.

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Nonspeech training

The study in Table 1 established that the trainees had an APD prior to training [6••]. These trainees showed significant improvements in their nonspeech test scores after training. This was not because of repeated testing or maturation because the untrained controls did not show the same gains. This suggests that nonspeech training can treat a nonspeech APD in children.

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Simple speech training

The study in Table 2 ascertained that trainees had an APD prior to training [6••]. It also found that trainees showed significant improvements in their simple speech test scores after training. This was not because of an effect of repeated testing or maturation because the untrained control group did not make the same gains. This suggests that simple speech training can treat a simple speech APD in children.

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Fast ForWord Language

One of the four FFW-L studies in Table 3 did not include any auditory tests [8••]. Two other FFW-L studies tested children on an auditory test before and after training but did not ascertain that they had an APD prior to training [9••,10••]. Both of these studies found a significant improvement in auditory test scores after training. One of these studies did not include an untrained control group, so we cannot tell if the auditory test gains were due to FFW-L or due to repeated testing or maturation effects [10••]. The other study did include an untrained control group who did not make similar gains in their brain responses to attended sounds [9••]. However, this study did not test if the children had an APD before training. So, this study cannot tell us if FFW-L had a genuine effect on abnormal auditory brain responses. The fourth FFW-L study did establish that trainees had an APD prior to training [7••]. However, it found that FFW-L had no effect on their APD.

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Tomatis therapy

Only one recent study has tested the effect of Tomatis therapy in children with a developmental disorder [11•] (see [12] for an excellent review of previous music-therapy studies). Unfortunately, this study did not test the trainees for an APD before or after Tomatis therapy. So, we cannot tell if Tomatis therapy treats APDs.

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Which auditory training programs treat specific language impairment, specific reading disability, autism, or attention deficit hyperactivity disorder symptoms?

The information in columns 7–13 of Tables 1–4 can also be used to determine which auditory training programs treat symptoms of SLI, SRD, autism, or ADHD.

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Nonspeech training

The study in Table 1 found that nonspeech trainees made no gains in their impaired nonword reading, irregular-word reading, nonword repetition, or attention after training [6••]. The nonspeech trainees did make significant gains in their sentence repetition. However, this was probably due to repeated testing or maturation because the untrained controls showed similar gains. Thus, nonspeech training does not seem to treat poor reading, poor spoken language, or attention in children.

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Simple speech training

The study in Table 2 found that trainees made no significant gains in their poor nonword reading, irregular-word reading, nonword repetition, or attention from before to after training [6••]. The speech trainees did make significant gains in the sentence repetition. However, this was probably due to repeated testing or maturation since the untrained controls showed the same gains. So, simple speech training does not seem to treat poor reading, poor spoken language, or attention in children.

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Fast ForWord Language

Two of the four FFW-L studies reported that trainees had poor reading prior to training. These trainees had significantly better reading after training [7••,8••]. In one study, this was probably due to repeated testing or maturation because the same effect was seen in untrained controls [8••]. This was not the case for the other study [7••]. So FFW-L has an inconsistent effect on poor reading.

All four FFW-L studies tested children on a variety of spoken language tests before and after training. In two studies, children had impaired receptive language scores before training [8••,9••]. These children showed significant gains in receptive language after training. In one study [8••], this improvement was due to repeated testing or maturation (i.e. the same improvement was seen in untrained controls). This was not the case in the other study [9••]. So, FFW-L also has an inconsistent effect on poor receptive language.

The same two studies found children with SRD or SLI had impaired expressive language scores before training. One study did not find an improvement in expressive language after FFW-L training [9••]. The other study did find a significant improvement in expressive language after FFW-L training; however, this was probably due to repeated testing or maturation since the untrained control group showed a similar effect [8••]. This suggests that FFW-L does not help impaired expressive language.

One study found that a group of children with SLI had impaired total language scores before training [10••]. These children's total language scores showed significant gains after FFW-L training. However, a control group who did placebo training (i.e. maths and science) showed a similar effect. Thus, the gains made in total language scores after FFW-L may have been due to a placebo effect, repeated testing, or maturation (see [13•] for a fascinating discussion of placebo effects).

Another study found that trainees had poor scores on two rapid naming tests before training [7••]. These children made significant gains on one of these tests after FFW-L. This was not due to repeated testing or maturation because an untrained control group did not show the same gain. Thus, FFW-L may treat some, but not all, forms of impaired rapid naming.

Finally, one study found impaired phoneme awareness in trainees before FFW-L [8••]. Trainees had significantly higher phoneme awareness scores after FFW-L training. However, this was probably due to repeated testing or maturation since untrained controls showed the same gains. Thus FFW-L does not appear to treat phoneme awareness.

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Tomatis therapy

The Tomatis therapy study [11•] focussed on receptive and expressive vocabulary in children with autism. It did not establish that the children had poor vocabulary to start with. However, it did report significant improvements in receptive and expressive vocabulary after therapy. Unfortunately, this study did not include an untrained control. So we cannot tell if the gains in vocabulary were due to a genuine effect of Tomatis therapy or due to repeated testing or maturation.

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Summary

The title of this article asks: can APDs be treated? Considered en masse, the results of recent studies that have run auditory training programs with children with SRD, SLI, and autism suggest that the answer is yes.

The question that follows is which auditory training programs treat APDs? Recent evidence suggests that nonspeech training and simple speech training treat APDs. Only one recent FFW-L study tested if trainees had an APD prior to FFW-L training, and this showed that children's auditory test scores were not better after FFW-L [7••]. The jury is out on Tomatis therapy since the only recent study did not test children for an APD before training [11•].

If nonspeech training and simple speech training treat APDs, then do programs that include nonspeech training and simple speech training treat the symptoms associated with SRD, SLI, ADHD, or autism? The recent data suggest not. Nonspeech training and simple speech training did not treat poor reading, poor spoken language, or attention. FFW-L may treat one form of impaired rapid naming, but it has inconsistent effects on poor reading and poor receptive language, no effect on poor phoneme awareness or poor expressive language, and has a placebo-like effect on total language scores. The Tomatis therapy study did not include an untrained control group so we do not know if the trainees' posttraining gains in vocabulary were a result of training, repeated testing, or maturation.

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Conclusion

The conclusion that nonspeech training and simple speech training treats APDs but does not treat poor reading, spoken language, or attention has practical implications for commercial auditory training programs, such as FFW-L, Earobics, Tomatis therapy, and Somatas therapy, that claim to help children with developmental disorders. For example, FFW-L trains children to process nonspeech sounds, simple speech sounds, and complex speech sounds (i.e. syllables, words, and sentences). If training nonspeech and simple speech processing has no effect on poor reading or poor spoken language, then whatever genuine effects FFW-L has on reading and spoken language must stem from training complex speech. If FFW-L removed the redundant nonspeech training and simple speech training, then children could achieve the same results in less time, or could achieve greater results in the same time. Further, removing 40% of the training should remove 40% of the cost (currently 1800–2600 USD + tax). This would make FFW-L more affordable to lower-income families and schools.

Given the popularity of auditory training programs like FFW-L, it is worrying that only two recent auditory training studies done with children with SRD, SLI, autism, or ADHD meet the criteria of a good treatment study. How are parents and clinicians – and perhaps most importantly the media – supposed to make sensible judgements about the efficacy of a commercial auditory program when there are so few good auditory training studies to refer to?

One solution is to teach parents, clinicians, and reporters how to sort the good auditory training studies from the bad ones. One approach might be to give people a checklist including the features outlined in the section: How should an auditory training program be tested? If they find a study that includes features 1–5, then they can be fairly sure that the results tell them if an auditory training program works better than no training. If they find a study that includes features 1–4 and 6, then they can be fairly sure that the results tell them if an auditory training program works better than another type of training. If they find a study with features 1, 2, 3, or 4 – but without features 5 or 6 – then they can be sure that they should view the results with great caution.

A second solution to the lack of good auditory training studies is to insist that scientists boost their efforts to conduct well controlled auditory training studies. At the very least, a study should include an untrained control group or a delayed training control group to measure the effects of repeated testing and maturation on the assessment tools (see [14] for a recent discussion on test-retest effects in training studies). Training studies without an untrained control group cannot tell us if a training program has a real effect on APDs or on SRD, SLI, ADHD, or autistic symptoms. Such studies should not be published because they are too often used by commercial marketing departments and ill-informed reporters as ‘scientific proof’ for a training program. This promotion is particularly worrying in light of the results of recent studies which suggest that children's APDs can be treated by nonspeech and simple speech training, but that this has little or no effect on the symptoms associated with SRD, SLI, ADHD, or autism.

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Acknowledgement

The author is an Australian Research Council (ARC) Research Fellow (DP0879556) and is supported by a National Health and Medical Research Council research grant (488518).

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References and recommended reading

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Papers of particular interest, published within the annual period of review, have been highlighted as:

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• of special interest

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•• of outstanding interest

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Additional references related to this topic can also be found in the Current World Literature section in this issue (pp. 000–000).

1•• Dawes P, Bishop DVM. Auditory processing disorder in relation to specific learning disabilities: a review and critique. Int J Lang Commun Disord (in press). This provides a very up-to-date, thorough, and well balanced review of the issues relating to the potential use of APD (CAPD) as an official diagnostic category.

2 McArthur GM, Bishop DVM. Auditory perceptual processing in people with reading and oral language impairments: current issues and recommendations. Dyslexia 2001; 7:150–170.

3 McArthur GM, Ellis D, Atkinson C. Atypical brain responses to sounds in children with language and reading impairments. Dev Sci (in press).

4 Sutcliff P. Comorbid attentional factors and frequency discrimination performance in a child with reading difficulties. Int J Disabil Dev Educ 2006; 53:195–208.

5 Cage N, Siegal B, Roberts TPL. Cortical auditory system maturational abnormalities children with autism disorder: an MEG investigation. Dev Brain Res 2003; 144:201–209.

6•• McArthur GM, Ellis D, Atkinson C, Coltheart M. Auditory processing deficits in children with reading and language impairments: can they (and should they) be treated? Cognition 2008; 107:946–977.

7•• Gaab N, Gabrieli JDE, Deutsch GK, et al. Neural correlates of rapid auditory processing are disrupted in children with developmental dyslexia and ameliorated with training: an fMRI study. Restor Neurol Neurosci 2007; 25:295–310.

8•• Given BK, Wasserman JD, Chari SA, et al. A randomised, controlled study of computer-based intervention in middle school struggling readers. Brain Lang 2008; 106:83–97.

9•• Stevens C, Fanning J, Coch D, et al. Neural mechanisms of selective auditory attention are enhanced by computerised training: electrophysiological evidence from language-impaired and typically developing children. Brain Res 2008; 1205:55–69.

10•• Gillam RB, Frome-Loeb D, Hoffman LM, et al. The efficacy of Fast ForWord Language intervention in school-aged children with language impairment: a randomized controlled trial. J Speech Lang Hearing Res 2008; 51:97–119. This is another excellent study of FFW-L. To its credit, it included three placebo-trained groups. All of the groups made similar gains on spoken language measures. This shows that FFW-L works no better (nor worse) than many other types of training including maths, science, and geography training.

11• Corbett BA, Shickman K, Ferrer E. Brief report: the effects of Tomatis sound therapy on language in children with autism. J Autism Dev Disord 2008; 38:562–566. This is the only recent study of music therapy done with children with a developmental disorder.

12 Sinha Y, Silove N, Wheeler D, Williams K. Auditory integration training and other sound therapies for autism spectrum disorders: a systematic review. Arch Dis Childhood 2006; 91:1018–1022.

13• Goldacre B. Bad science. London: Fourth Estate; 2008. This is an entertaining and very informative discussion about the history and importance of placebo effects.

14 McArthur G. Test-retest effects in treatment studies of reading disability: the devil is in the detail. Dyslexia 2007; 13:240–252.

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Keywords:

auditory processing disorder; auditory training; autism; specific language impairment; specific reading disability

© 2009 Lippincott Williams & Wilkins, Inc.

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