Slides from a talk given at University of Western Australia on Tuesday 2nd October 2012, This lecture was co-hosted by the ARC Centre of Excellence in Cognition and its Disorders and the Institute of Advanced Studies, University of Western Australia

1. Neurodevelopmental disorders: are our
current diagnostic labels fit for purpose?
Dorothy Bishop
Wellcome Principal Research Fellow
Department of Experimental Psychology
University of Oxford

2. Meanings of ‘neurodevelopmental
disorder’
 Neurological disorders with known prenatal
cause (genetic or acquired)
 e.g. Williams syndrome, fetal alcohol syndrome
 Disorders where abnormal neurodevelopment is
inferred: actual cause is complex or unknown
 e.g.developmental dyslexia, autistic disorder, specific
language impairment (SLI), developmental
coordination disorder (DCD), developmental
dyscalculia
2

3. Common characteristics of
neurodevelopmental disorders
 Defined in terms of behaviour
 Often use medical terminology, drawing parallel
with acquired disorders
 Tend to be familial
 No single biological cause
 Male preponderance in most
3

4. Do children fall neatly into these
categories?
4

5. Kaplan et al, 2001
• Sample of 179 children
and families recruited from
clinics, special schools
Developmental co-ordination • All had dyslexia and/or
disorder, 17% ADHD
• Comprehensive
assessment for ADHD,
dyslexia, DCD, and
psychiatric disorders
ADHD, 65%
Dyslexia, 70%
“Comorbidity is the rule, not the exception”
Gilger and Kaplan, 2001

6. Western Australian study
608 children aged 3 – 14 years
 449 Typically-developing
 30 Autism spectrum disorder (ASD)
 24 Mental retardation (MR)
 30 Receptive-expressive language disorder (SLI)
 22 Developmental co-ordination disorder (DCD)
 53 Attention deficit hyperactivity disorder (ADHD)
 Assessments of IQ, language, motor, attention,
social cognition, executive function
Dyck, M. J., et al. (2011). The validity of psychiatric diagnoses: The case of
'specific' developmental disorders. Research in Developmental Disabilities,
32(6), 2704-2713.

7. Dyck et al: Discriminant function analysis
Typical
Autism
MR
SLI
DCD
ADHD

8. Same child, different diagnosis
 Educational psychologist:
Dyslexia
 Speech-language pathologist: SLI
 Psychiatrist: Autism spectrum
disorder (ASD)
 Neurologist: Developmental
co-ordination disorder (DCD)
 Paediatrician: ADHD

9. Questions
 Are these valid diagnostic categories?
 What is the impact of labels?

10. Public perception of diagnostic label
 Explanatory force
 Symptom complex
x Qualitatively distinct from other disorders
 Known cause

11. Which is true?
 He can’t read because he has dyslexia
 Dyslexia is a term applied to children who
find it hard to read for no obvious reason
cf. Erythema

12. Distinctive symptoms?
Rutter and Yule (1975)
 No clustering of the developmental anomalies that are
said to characterize dyslexia.
• "In short, there has been a complete failure to show that
the signs of dyslexia constitute any meaningful pattern."
p 194
• "If there is no recognisable pattern, then in the present
state of knowledge there is no means of determining
whether anyone has the hypothesized condition. Some
kind of biological 'marker' would be needed and so far
none has been found."

13. Distinctive symptoms?
Stanovich (1994)
 Poor readers very similar
cognitive profiles, regardless of
IQ
 Same phonological core deficit
in both high and low IQ

14. Twin Study Method
Twins growing up together are expected to resemble each other
MZ twins: genetically identical
DZ twins: share 50% of polymorphic
genes
Question:
Is concordance for disorder higher
in MZ than in DZ twins?
Most studies of dyslexia find YES
Grigorenko, E. L. (2004). Genetic bases of developmental dyslexia: A
capsule review of heritability estimates. Enfance, 56, 273-288.

15. A recent study shows that variations in a gene called DCDC2 may disrupt
the normal formation of brain circuits that are necessary for fluent
reading, leading to dyslexia. After further research, genetic screening
for these variations could identify affected children early in their
lives and possibly prevent the misdiagnosis of other learning disabilities
that resemble dyslexia.
“We have good statistical data that variations of the DCDC2 gene are
strongly associated with reading disability, also known as dyslexia. These
results reconfirm that dyslexia is strongly genetic and is not a
consequence of just environmental factors,” says lead investigator
Jeffrey Gruen, M.D., Associate Professor of Pediatrics at Yale University
School of Medicine in New Haven, Connecticut.
15

16. So is it like this?
Copyright: www.CartoonStock.com

17. High heritability
≠
Single major gene
17

18. Genetics: Reality check
 DCDC2 is one gene that has been associated
with dyslexia in several studies
 Scerri et al (2011) found a SNP on this gene
where the association was significant at p = .005
 The risk allele was found in:
• 23% of controls
• 31% of dyslexics

19. General population sample
100 children
10% dyslexic
90 OK 10 dyslexic
23% 31%
Risk variant Risk variant
* *
21 69 3 7
With risk variant
• Most people with the ‘risk’ allele won’t have dyslexia
• Most people with dyslexia won’t have the risk variant

20. Brain biomarkers
20

21. BBC website on Dyslexia

22. Brain regions found to differ
structurally in dyslexics vs normal readers
• Corpus callosum size
inferior frontal precentral gyrus (motor control) • White matter gyral
gyrus (speech depth
production) • Right cerebellum grey
matter
• Auditory cortex size
• Precentral gyrus grey
matter
• Pars triangularis, frontal
lobe, size and shape
• Asymmetry of planum
auditory cortex temporale (> and <)
(hearing) • Sylvian fissure
length/position
cerebellum
(automatisation of skill)
• Temporo-parietal white
matter microstructure
• Relative proportion of
frontal and posterior
N.B. Much within-group variation cortex

23. Functional brain imaging

24. Children with
reading disability
display under-
activation of
a network of left-
lateralized areas
during reading,
including
occipito-temporal,
temporo-parietal,
and inferior frontal
cortical regions
Shaywitz, 2003

25. Cause or consequence of
reading problems?

26. Experience affects the brain
 Dehaene et al, 2010: compared:
 31 schooled/literate adults
 22 unschooled ex-illiterate adults
 10 unschooled illiterate adults
 All from Brazil or Portugal

27. Activation of visual word form area by written words
literate
ex-illiterate
illiterate

28. Activation of language areas by spoken language
Literate
Ex-illiterate
Illiterate

29. Implications for functional imaging studies
of dyslexia
Dyslexic-non-
dyslexic differences
could be
consequences of
poor reading, rather
than causes

30. Public perception of diagnostic label
x  Explanatory force
x  Symptom complex
x  Qualitatively distinct from other disorders
x  Known cause

31. General issues for neurodevelopmental
disorders
SLI
ASD dyslexia
ADHD
 Overlap at behavioural level
 Also overlapping causes and neurobiology

32. One alternative
 Broad category of ‘neurodevelopmental disability’ to
establish need for services
 ‘Disability’ emphasises impact on individual
 ‘Neurodevelopmental’ emphasises biological basis: not
just poor teaching
 Supplemented with assessment to establish profile of
difficulties/strengths on different dimensions, and
determine which services to prioritise
http://deevybee.blogspot.com.au/2010/12/whats-in-name.html

33. Advantages
 Avoids need for multiple diagnoses
 Encourages multidisciplinary assessment
 Avoids misleading notions of medical syndrome

34. Disadvantages
 Labels such as dyslexia, autism, ADHD now
well-established; provide useful nexus for
support groups, etc.
 Widespread tendency to assume that if there
isn’t a medical label, there isn’t a serious
problem
• The problem is just a ‘social construct’ or
worse still, an ‘excuse’

36. Sternberg & Grigorenko
Our Labeled Children (1999)
 Schools have financial interest in identifying
specific learning disabilities
 Teachers “let off the hook”; "Often, the problem
is not what is being taught but how it is being
taught"
 “.. diagnosis as it now exists has provided some
children who seem to be underachieving, based
on their socioeconomic status, a way out"

37. Labels can be helpful: but how to
choose them?

38. A tale of two disorders
DEVELOPMENTAL DYSLEXIA SPECIFIC LANGUAGE
IMPAIRMENT
 Unexpected difficulty in
learning to read  Unexpected difficulty in
learning to talk
 Not explained by lack of  Not explained by lack of
opportunity to learn opportunity to learn
 Not explained by  Not explained by
visual/hearing problems, low visual/hearing problems, low
IQ IQ
 Not due to brain damage or  Not due to brain damage or
known syndrome known syndrome
(DEVELOPMENTAL DYSPHASIA)
(SPECIFIC READING DISABILITY)
Prevalence 3-7%
Prevalence 5-10%

39. Dyslexia/SLI – good and poor memes
“Why is it more desirable to have dyslexia than to
have a reading disability?
Why does no one other than speech-language
pathologists and related professionals seem to know
what a language disorder is?
Why is Asperger’s syndrome, a relatively new disorder,
already familiar to many people?”
Kamhi, A. G. (2004). A meme's eye view of speech-language
pathology. Language Speech and Hearing Services in Schools,
35(2), 105-111.

40. Memes: What Are They?
“Examples of memes are tunes, ideas,
catch-phrases, clothes fashions, ways of
making pots or of building arches. Just
as genes propagate themselves in the
gene pool by leaping from body to body
via sperms or eggs, so memes
propagate themselves in the meme pool
by leaping from brain to brain via a
process which, in the broad sense, can
be called imitation.”
R. Dawkins

41. Successful meme
 Easy to understand, remember, and
communicate to others:
 May be influenced by whether confers
advantage to the person communicating
 Survival does not depend on whether they
are useful, true, or potentially harmful

42. Dyslexia has survived many attacks!
Terminology in published papers
Dyslexia
Specific reading disability
Specific reading retardation (Rutter & Yule)
Developmental reading disorder (DSMIV)
1985-1989 1990-1994 1995-1999 2000-2004 2005-2009

43. Amount of research (1985-2009) and prevalence
of neurodevelopmental disorders
papers freq.
Condition /year %
Tourette syndrome 83 0.5
Autistic spectrum disorder 643 0.7
Developmental dyscalculia 9 3.0
Attention deficit hyperactivity disorder 505 5.0
Developmental dyslexia 152 6.0
Developmental coordination disorder 16 6.5
Specific language impairment 46 7.4
Bishop, D. V. M. (2010). Which neurodevelopmental disorders get
researched and why? PLOS One, 5(11), e15112. doi:
10.1371/journal.pone.0015112

44. Research funding and frequency of
neurodevelopmental disorders
NIH spend $
Condition 2000-2009 freq. %
Tourette syndrome 252,709,203 0.5
Autistic spectrum disorder 2,613,298,181 0.7
Developmental dyscalculia 4,355,095 3.0
Attention deficit hyperactivity disorder 2,205,461,058 5.0
Developmental dyslexia 136,012,937 6.0
Developmental coordination disorder 4,093,060 6.5
Specific language impairment 125,035,522 7.4
44

45. Labels have consequences
 Medical-sounding labels get taken seriously
 Conditions with medical-sounding labels attract
more research funds
• But not always successful: dyscalculia and dyspraxia
have not been successful memes
• May also depend on the professional group with
principal responsibility (power, gender)
 And a good meme may include or even induce
positive features of disorder

46. Positive connotations of labels
So as I’m reading the narration into
a tape recorder, it started
to dawn on me. I’m not lazy. I’m not
stupid. I’m dyslexic!”
Henry Winkler
neurodiversity.com
Autism in Positive Light

47. In conclusion
 Naïve to imagine we could abandon terms such as
‘dyslexia’
Adverse consequences would include:
 Fewer children having problems recognised
 Increase in tendency to blame all problems on poor
parenting/schooling
 Less research into biological bases
 But need to be aware this (and other
neurodevelopmental disorders!) is a fuzzy category, and
does not explain anything
 Children need multidisciplinary assessment
 Question of what to do about ‘cinderella’ conditions: SLI,
dyscalculia, dyspraxia

48. Raising Awareness of Language Learning Impairments
http://www.youtube.com/RALLIcampaign

49. Dorothy Bishop
Oxford Study of Children’s
Communication Impairments,
Department of Experimental
Psychology,
South Parks Road,
Oxford,
OX1 3UD,
England.
dorothy.bishop@psy.ox.ac.uk