Please enable JavaScript.
Coggle requires JavaScript to display documents.
Developmental Lang Disorder (Behaviour (Different labels, Different…
Developmental Lang Disorder
Behaviour
Overt characteristics that define disorder
What is DLD?
Bishop et al (2016)
Child's lang abilities = below chronological age expectation
Difficulties = severe/persistant > interfere with everyday life
Not explained by other developmental concerns (sensory impairment, autism, extreme deprivation, head injury, global deve delay)
Lang impairment = freq associated with other developmental concerns
Expressive vs receptive, production vs comprehension
Phonology = sounds of lang + way used (often resolve)
Heterogeneity - very variable
Syntax/morphology = rules that control sentence formation/word endings (plural, past tense, grammar)
Semantics = meaning of individual words/in context
Pragmatics = use of lang in context & social exchanges (narrative/discourse)
Different labels, Different criteria
Confusion
Developmental lang dis
Speech, lang and communication needs education
DSM-5: lang dis
Behaviourally defined disorder
Give test > have SD cut off in different domains to meet criteria
Dependent on task, aspects of lang, cut-off?
Bishop (2014)
Domains other than lang have consistent diagnosis terminology
Unsustainable, causes confusion, impedes research/access to services
Needs consensus
DSM 5 > lang disorder = too broad
Specific lang impairment (primary ang impairment, deve lang dis, lang learning impairment)
Clinical Markers
More efficient?
Better way to understand quickly
Large effects - achievement, self esteem, etc.
Sometimes hard to notice
Search for clinical markers
Past Tense Elicitaion
Generate past tense from present
Often hard for children with DLD
Pictures + sentences
Nonword repetition
Children's nonword repetition test
Increasing number of syllables
Bishop et al (1996)
Lang impaired = worse ability
Phonological skills
Sentence repetition
Repeat sentence
increasing length and grammatical complexity
Most sensitive > maybe follow up with something more comprehensive
Current View
Ideally parent interview, observation, detailed assessment of lang
Should be taking more holistic view - multiple sources of info
E.g. ADHD, ASD, dyslexia
DLD vs SLI
SLI = specific - attracts more support/resources, unfairly advantaged
SLI = most commonly used research term
DLD ~ SLI, BUT
Specific - non verbal ability/IQ
Truly specific = rare/transient
Lang profile + genetic risk similar for SLI and NLI
Nonverbal ability doesn't predict response to intervention
DLD = preferred (heterogeneous)
Bishop (2004)
DD + SLI
Thought to be distinct
Now different manifestations of same underlying problem
Underestimates independent influence of semantic/syntactic deficits
Two dimensions impairment needed
Variable Phenotype
Identifies 7% of pop. at school entry as having large impairment
1 yr later = 46& met criteria
1/3 of children identified has bee referred/seen by speech and lang therapists or were causing concern
No phonology or pragmatic measures
No measures of 'impact' or functional impairment
Tomblin, Records & Zhang (1996)
Comprehensive view of lang
Expression - vocab composite, grammar composite, narrative composite
Comprehension - comprehension composite, expression composite
Modality = picture identification, picture naming, grammatical understanding, grammatical production, narrative understanding, narrative recall
Aetiology
Genetic + governmental influences that shape brain deve, cog, beh
Family Aggregation
Genetic loading
Rates of lang difficulties higher in relative of those with SLI, compared with controls
Families share same environment as well as genes so can't distinguish aetiology
Lang differences do tend to run in families
Twin Stuides
Monozygotic - Identical, 100% genetic material
Dizygotic - nonidentical, 50% genetic material
Hypothetical situations
Shared environments - perfect concordance between both twins
Genes - Perfect MZ, 50% DZ
Unique enviro - concordance low in both
Method
MZ twins = genetically identical, DZ twins = share 50% of polymorphic genes
Concordance higher in MZ than DZ?
Suggests genetic loading > estimate regarding importance of genes
Estimates vary with tasks, age ps, sample size, nature of sample
Heritability
Bishop + Hayoiu-Thomas (2007)
Heritability estimates for SLI = inconsistent
Method influence result > higher heritability is SLI defined in terms of referral to speech/lang pathology rather than lang test scores
Speech difficulties = major role
Childhood lang disorders = identified by population screening are likely to have different phenotype/etiology from clinically referred cases
Genetic studies = more likely to find high heritability if focus on speech difficulties + referred for intervention
Risk Factors
Not deterministic
Genes
Lots of environmental risk factors
Male
Family history of DLD/dyslexia
Low parental education
Poverty > low SES = strong
Molecular genetics
Difficult to establish in phenotypic noise
Linkage to chromosomes 16 (non-word repetition deficits) and 19
FOXP2
Chromosome 7
Implicated in severe of familial lang impairment
Not implicated in more typical forms of SLI
CNTNAP2
Downstream target of FOXP2
Implicated in lang abilities across range of neurodevelopmental disorders
Not consistent/don't fully explain
Tracking down associated genes
Compare lang scores of people with different genotypes
Newbury et al (2009)
- two genes of chromosomes 16 associated with poor phonological STM in a lang impaired sample
'Risk' alleles common in general population and have small effect size
Many genes of small effect > complex abilities therefore unlikely it is one gene
Neurobiology
Neural Substrate
Perisylvian regions core to ang function in adult brain
causally implicated in acquired disorders - cog neuropsycholgy
Damage to core lang regions in brain > KE family (YES) speech + lang impairments in 50%, but unusual?
Not necessary or sufficient for DLD
Typicalities don't necessarily lead to disorders
Are neuroanatomical correlates of developmental (vs. acquired) lang disorders more widespread?
Karmiloff-Smith (1998)
: neuroconstructivism
Lang is supported by whole brain + certain areas = specialised
Across the brain
Differences in brain structure/function that are associated with particular disorders
Herbert et al (2003)
N = 54: 24 DLD, 30 controls
5-11 years
Quantitative volumetric whole-brain analysis (size)
DLD brains: modestly larger, most robust findings is larger cereal white matter
This counters modular arguments + more consistent with neurocontructivist ideas
Contrasting findings: generally reduced size
Not specific to DLD > seen in other deve disorders
Brain Asymmetry + lang impairment
Decreased size of left hemisphere lang structures
Most studies - reduced/reversed asymmetry in children with lang/literacy problems
Some evidence for developmental failure to 'lateralise; lang to the left hemisphere
BUT
Research characterised by inconsistencies
Small sample sizes
Lack of agreed definition
Recent consensus may help
Causation
Subtle rather than gross differences
Effects not universal or specific to DLD
Leonard et al (2006)
DD = isolated reading deficits
SLI = poor receptive + expressive oral lang skills
Results
Smaller/symmetrical brain structures = severe comprehension impairments (SLI)
Larger/asymmetrical brain structure = poor word reading w/ relatively preserved comprehension (DD)
Best performance = anatomical risk zero
Sig comprehension deficits in distinguishing DD from SLI
Reading impairments with/out comprehension deficits = atypical neuroanatomical domains
Cognition
Differences in how children perceive + think about the world
Modular Theories
DLD due to specific deficit to innate lang module
Against
Changes over time therefore NOT static
Refute modularity
Perceptual Theories
Auditory processing deficit
Children with DLD are impaired in their ability to discriminate rapid, brief tones of different freq
Can't process sounds well therefore difficulty in phonology
Require longer processing times to discriminate, sequence, and remember brief stimuli when followed by another stimulus
Cohen et al (2005)
Tested auditory porcessing hypothesis
Fast forward > Intensive training in discrimination/understanding, gradually reducing modification until child can do task at normal speech presentation
77 children, 60-10 years: Treatment, Active control, Treatment as usual
Intervention: 90 minute individual session, 5 times a week for 6 weeks
No evidence that it works - despite grand claims
FFW is expensive and labour intensive
Auditory processing deficits neither necessary nor sufficient to cause SLI
Processing limitation theories
Lang involves processing difficult inputs
Generalised slowing hypothsis
Miller et al (2001)
SLI = 29, Control = 29, NLI = 19
10 processing tasks
SLI, NLI slower than controls
Greater slowing for NLI
Not universal or specific
Procedural deficit hypothesis
Learn certain items go together which aids learning
Ullman + Pierpont (2005)
: not specific problem with lang, but with learning any rule based motor sequences
Procedural learning underpins rule governed tasks that involve implicit, sequence learning
Lang like this? Grammar/phonology are: rule governed, learned implicitly, involved motor sequences
SLI (DLD) could arise from impairments to procedural memory circuits in the brain
Procedural learning (implicit learning)
Lum et al (2010)
: Sequence learning > SLI = longer RTs
West et al (2018)
: Hebb learning task
Controversial
Implicit learning tasks = unreliable/insensitive to IDs
Does not correlate with lang ability
Hsu + Bishop (2014)
Comparing motor procedural learning + implicit verbal sequence learning tasks
SLI, typical age matched, younger typical receptive grammar matched
SLI
Same level as grammar matched
Poorer than age matched
Motor procedural (not learning sequential relationships)
SLI = comparable to age matched, better than grammar matched
Poor implicit learning of word sequences in verbal memory task SLI
SLI characterised by deficits in learning sequence-specific > Not generally weak procedural learning