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Auditory Processing Disorders Acquisition Treatment

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									ASHA Annual Convention Session 0432: Auditory Processing Disorders: Acquisition and Treatment
Dave Moore
MRC Institute of Hearing Research University Park Nottingham NG7 2RD

www.ihr.mrc.ac.uk

Outline
•Auditory processing disorder (APD): definitions & importance •Brain plasticity – inheritance and experience •Auditory deprivation – effect on the brain

•Effects of OME – evidence for APD
•Nature of APD – diagnosis and relation to cognition •Is APD due to inheritance or experience? •Auditory training improves essential listening skills •Auditory training and the management of APD

Auditory processing disorder (APD)
Definitions
By default: A problem with listening that can’t be explained by tests of peripheral auditory function, notably, audiometry. Alternative: Listening disability resulting from impaired brain function and characterised by atypical recognition, discrimination, grouping, ordering or localisation of nonspeech sounds (BSA working party, 2004).

Relation to other disorders
Dyslexia Specific Language Impairment Autism ADHD Behaviour Problems

} }

20-50% comorbidity? reports of comorbidity

Brain plasticity – inheritance and experience
Frequency representation (% from high frequency end)

Neural pathways generally grow directly to the correct targets. Typically, there is some exuberant growth that is lost during development. In some cases (e.g. visual cortex) this has been shown to be dependent on sensory experience
This figure shows the development of projections from the cochlea to the cochlear nucleus (CN). A small section of the basal cochlea was labelled with a tracer, and the representation of that section was then examined in the anteroventral (AVCN) and dorsal (DCN) CN. The cochlea was over-represented in the adult brain, shown by the spread of colours, and further overrepresented in the infant AVCN (by 53%) and DCN (by 32%).

Infant
0
AVCN DCN

Adult
CN

20

40

60

80

100

(Adapted from Rubel and Cramer, J Comp Neurol, 2002; based on data from Leake et al, J Comp Neurol, 2002)

Auditory deprivation impairment
Conductive hearing loss can reduce resting neural activity in the central auditory system
At left, the level of metabolism is reduced in the right inferior colliculus (IC) following removal of the malleus in the left ear
(from Tucci, Cant and Durham, Hear Res, 2001)

Conductive loss can also change brain connections
At right, the direct projection from the CN to the IC on the side opposite an ear plug is increased as a result of long term plugging
(from Moore et al, J Neurosci, 1999)

IC

IC

CN

CN

Plug

LEFT COCHLEA

RIGHT COCHLEA

Otitis media with effusion (OME)
OME both attenuates and delays sounds entering the inner ear
Loss (dB) Time (μs) Delay Advance
0
20 40

Middle ear effusion
OME occurs at least once in almost every child before the age of 5. 15% of children have OME in 1 or 2 ears for ≥ 50% of their life to age 6.

+50 -50

-150

-250

1

2

4

8

16

Stimulus frequency (kHz)
(from Hartley and Moore, Hear Res, 2003)

OME during infancy impairs binaural hearing
We tested binaural hearing using the masking level difference (MLD) in children whose lifetime history of OME was known

31 children aged 6;8 (s=0;5) y.o. were followed from birth with monthly tymps and otoscopy. All children were OME free at MLD testing Masking level difference (dB)
20 16 12 8 4 0

A ‘threshold’ level of OME, ~45% prevalence over the first 6 years, led to significantly reduced MLD
Adults had larger MLDs than the lower OME prevalence children, but the highest OME prevalence group (7/31) had smaller MLDs than their agematched peers
(from Hogan and Moore, JARO, 2003)

Low

High
2 3 4

Adults 1

OME Quartile Children

Binaural hearing recovers after OME
20

Masking level difference (dB)

p<0.0005

15

10

5

0

Control OME

Control OME

1989

1996

In earlier studies we showed that reduced MLD in younger children recovered when the same children were tested 7 years later. This suggested a form of binaural relearning

Children (6-12y.o. in 1989), referred with chronic OME, were matched with OME-free Controls. All children were OME free at MLD testing
(from Moore et al., Audiology, 1991; Hogan et al., Audiol. Neuro-Otol, 1996)

APD – Diagnosis
Backward Masking Frequency Discrimination Temporal Integration

Auditory Filter Width

We are using a ‘population’ approach. Since we do not know how to diagnose APD, we are obtaining performance data from random samples

Time

75 children (6-11y.o.) have been tested on a large battery of audiological, psychoacoustic, cognitive and speech-in-noise tests. We are shortly moving to a multi-centre study (1600 children) using a reduced battery.
Frequency discrimination – track failure

Threshold (dB SPL)

Notch Noise – ‘Genuine poor performer’

Threshold (Δ%)

100 80 60 40 20 0 0 10 20 30 40 Mean ± 2 s.d.
Track 1 Track 2

Freq

100
Track 1 Track 2 Track 3

low variabili ty

10

0

10

20

30

40

Trials

Trials

Poor performers have been identified as ‘genuine’ (consistent) or, more commonly, ‘inattentive’. Both are candidates for APD

Children tested on two successive adaptive tracks using 3 interval odd-one-out tasks

APD – Relation to cognition & audiology
Age (years) # tasks poor performance 1 2 3 6-7 (n=25) 4 4 3 8-9 (n=25) 5 1 10-11 (n=25) 1 -

Poor performers were more common in younger age groups

Defined as AP threshold >2 s.d. from age mean or track failure. No association with hearing level or speech-in-noise

7
65

1

-

Poor performers Others 25 20 Poor performers Others

IQ (standardised)

60
55 50 45 40

OAE SNR (dB) Verbal IQ Non-verbal IQ

15 10 5 0

1kHz

4kHz

Poor performers had lower verbal IQ and reduced OAE amplitude and SNR
Non-verbal IQ matched typical performers. Frequency discrimination and resolution correlated significantly with phonological awareness, but not reading or memory

Is APD inherited or acquired?
Reasons for thinking APD is mainly inherited:
•Language impairment and dyslexia, with which APD is closely related, are highly heritable •Crucial aspects of AP (binaural hearing, fine temporal processing) involve unique potassium channels in the brainstem •Genes have been identified (in mice) that specifically affect central AP

Data suggests AP may be largely acquired:

-2.5 -2

Heritability of AP & Language Skills
Proband (LI) Co-twin

•Performance on the Tallal auditory repetition task (ART) and the Children’s Non-word repetition task (CNRep) has been compared in a study of monozygotic and dizygotic twins •APD (ART z-score < -1) and language impaired (CNRep z<-1) ‘probands’ were compared with their better performing co-twins on each test •Co-twins did not differ significantly on the ART, suggesting no or low heritability. In contrast they did differ on the CNRep, confirming the heritability of language impairment

z-score

-1.5 -1 -0.5 0
MZ
(n=36)

DZ
(n=27)

MZ
(n=36)

DZ
(n=24)

ART

CNRep

MZ – monozygotic, DZ – dizygotic twins

(Data from Bishop et al, JSLHR, 1999)

Auditory training improvement
20

Tone difference (%)

10 5

Each line shows a separate (adult) trainee

2

1

0.5

0.2 1

Practice block # (500 trials/block)
block #

2

3

4

5

6

7

Adult volunteers practiced pure tone frequency discrimination (FD) for 3500 trials (about 3½ hours over 4 days)
FD initially varied greatly, despite all listeners having ‘normal hearing’ FD improved quickly FD improved most markedly in those who started poorly

(from Amitay, Hawkey and Moore, Percept. Psychophys. 2005)

Training on difficult tasks works best
Amount of FD learning
0.5 0.4 0.3 0.2 0.1 0 Impossible Very difficult

Even an impossibly difficult training task (all 3 tones the same!) produced a high level of learning
Difficult Very easy

Task difficulty

Adult volunteers were tested for FD before and after 800 trials of training

FD was improved about equally by tasks ranging from moderately difficult to impossible FD was improved less well by tasks that were very easy (every trial correct)
(from Amitay, Irwin and Moore, Nature Neurosci. 2006)

Training includes bottom-up and top-down components
Amount of FD learning
0.5 0.4 0.3 0.2 0.1 0 FD Training (1 kHz)

No Tetris (no Passive training sound) (1 kHz)

Training task

FD Training (4 kHz)

Training received input from sharpening of tuning (bottom-up), task- and condition-specific attention, and general arousal (topdown)

Adults were tested at 1 kHz for FD before and after 800 trials of training (. . . or equivalent time without training)

FD was improved by all training tasks, including playing Tetris without sound FD was improved less well by training on stimuli other than the 1 kHz tone used for testing
(from Amitay, Irwin and Moore, Nature Neurosci. 2006)

Training improves essential language skills
Phoneme discrimination training (‘Phonomena’)
14

p<10-5

Trained Untrained

(see mindweavers.com)

Age Equivalent (yrs)

13 12 11 10 9 8 7 6 Pre Post

Training improved phonological awareness (rhyme, alliteration, Spoonerisms, non-word reading) by 2.3 years.

Time of Test

Delayed

8-9 y.o. mainsteam children were trained for 6 hours over 4 weeks Word listening (phonological awareness) was measured before and after training using the Phonological Assessment Battery (NFER-Nelson)
Training was maintained during 5 weeks before ‘Delayed’ testing
(Moore, Rosenberg and Coleman, Brain Lang 2005, 94, 72)

Summary
•Auditory processing disorder (APD): definitions & importance •Brain plasticity – inheritance and experience •Auditory deprivation – effect on the brain

•Effects of OME – evidence for APD
•Nature of APD – diagnosis and relation to cognition •Is APD due to inheritance or experience? •Auditory training improves essential listening skills •Auditory training and the management of APD

www.ihr.mrc.ac.uk

OME •Sarah Hogan

www.mindweavers.com

Language training •John Coleman •Joy Rosenberg

APD •Melanie Ferguson •Justin Cowan •Sally Hind •Alison Riley Training •Sygal Amitay •Dave Hawkey •Amy Irwin


								
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