Language, its development and pathologies
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Language, its development and
pathologiesIsabelle Rapin
Pediatric Neurology Seminar, Dec. 4, 2013
No conflict of interest
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Tools to investigate brain basis of behavior
Behavioral observation, neuropsychology Brain lesions, diseases Inhibitory rTMS (transient virtual focal lesions) Histology (incl. focal gene expression) Structural imaging: CT, MRI, DTI (connectivity) Metabolism: PET (glucose, metabolites,
transmitters) ↑ blood flow during task : fMRI (BOLD) Electrophysiology: EEG, ERP Magnetoencephalography
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Some advantages/drawbacks of these tools
All: group data, comparisons, baseline problem
Electrophysiology/MEG: real time data EEG/ERP: good time, poor spatial resolution MEG: realtime, subcortical data, expensive
and not widely available fMRI: reasonable spatial but not time
resolution. Most require cooperative subj., but advantage of clever experiments.
PET: radiation, etc.
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Language in the brain
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What is language?
In the individual: A computational system between thought and an acoustic signal (Hickok, 2006)
Among people: A shared medium to transmit information
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Multiple language modalities
(all: sensory → code/grammar → motor) Oral – speech
Written – reading, writing Gestural – Sign Somatosensory - Braille Mathematical notation Chemical, genetic symbols, etc. Musical notation Dance notation Blue prints Etc., etc.
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Levels of language
Phonology - sound units of language Grammar/syntax - word order, word
markers [morphemes], grammatical [closed class] words
Semantics - interface of (known) words – lexicon - to meaning
Pragmatics - communicative intent, verbal, non-verbal (prosody, gestures)
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Steps in language processing
Input Output (sensory) (motor)
Decoding Higher order Encoding processing
Input Output (sensory) (motor)
Decoding Higher order Encoding processing
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Steps in language processing
Input: sound to language (phonetics) Decoding input: phonological form +
lexical/semantic information Comprehension/programming: grammar,
sentence. Working verbal memory, executive skills, attention…
Programming output: lexical item + phonological form
Output: motor, i.e., speech, other language modalities
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Classic view: Language areas in the left hemisphere
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Classic view: Language connectivity: left hemisphere
Peoppel et al., 2012
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Current view of language in the left hemisphere
Dorsal stream
Dorsal stream Map sound to articulation
Ventral stream Map sound to meaning
Gow 2012
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Language Processing Circuitry
Primary auditory cortex (Heschel gyrus) ↔ Post. sup. temporal gyrus/sulc. (Wernicke) Ventral lexicon (post. middle temp. gyr. ↔
temporal pole (semantic hub) Ventral stream ↔ inf. frontal (Broca) Dorsal lexicon (inf. parietal, supramargin.
gyr.) Dorsal stream ↔ premotor cortex and ↔ Broca
(phonological loop, rehearsal – work. memory)
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Schematic of language processing:current view
Hickok 2009
1 2.
3..
3.
4.
4.
5.
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Functional language processing:
dorsal and ventral streams
ATI Ant.temporal lobe PM Premotor cortex
BA Broca area SMG Supramarginal gyrus
AUD Auditory cortex Spt Syvian parietal (Left only
MTG/ITG Middle/inferior temporal gyrus STG Superior temporal gyrus
Hickok 2009
A
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Interhemispheric language processing
Audition –sound → phonetic: bilateral Dorsal pathway -- phoneme and
articulation: left Ventral pathway – map sound to meaning:
left >> right Map words to thoughts (syntax, sentence):
bilateral distributed network Map communicative intent (pragmatics):
right
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Lateralization of phonologic tasks
(meta-analysis of neuroimaging studies)
Left RightVigneau et al., 2011
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Lateralization of lexical semantic tasks
(meta-analysis of neuroimaging studies)
Left Right
Vigneau et al., 2011
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Lateralization of syntax, sentences
(meta-analysis of neuroimaging studies)
Vigneau et al., 2011
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Interfaces of language with short term/working memory
Auditory buffer (aud. assoc. cortex) ↔ Prefrontal cortex ↔ perirhinal cortex,
hippocampus ↔ temporal cortex (working memory + episodic-semantic memory) (ventral stream + fornix & mammillo/ thalamic cingulate connections)
Ventral interconnects dorsal stream (articul.)
Child & Benarroch, Neurology Nov. 19, 2013Battaglia et al., Neurosci. Biobehav. Rev. 2012
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Language development
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Hearing is present in utero
Cochlea is full size by the end of the second trimester
Infant hears in utero, e.g., mother’s heart beat, borborygmi, voice
Hearing acuity good and testable at birth, matures during the first year
Latency of obligatory auditory ERPs decreases with maturation
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Sequence of language development
Phonology: at birth, function of language exposure → bilingual advantage
Pragmatics: at birth Semantics: starts at ~6 months Syntax: by ~ 2 years Reading: starts at preschool
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Stages of language development
Neonate – hears speech sounds relevant to all languages, hones the ones heard, loses others
~ 1 year -- Single word holophrastic utterances ~ 18-24 mos. – start of 2 word utterances,
mostly rote echoes ~ 24-30 mos. – 2 word utterances increase,
become individualized, start of grammatic rules ~ 3-4 years – sentences of increasing
complexity Fully mature syntax -- → ~age 10 yrs or more
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Semantic development Infants develop awareness of
permanence in the face of transformation (sounds, moving faces, objects, movements, own body parts)
Infants associate speech sounds with permanent stimuli
By 1 year: they understand some words, point to say “gimme” or “look”, may have a few meaningful words
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Syntactic development
Starts at the 2 word stage, usually around 2 years
Two word stage usually starts when toddler has some 50 words in lexicon
Sentences with articles, pronouns, and, later, morphologic markers, usually established by 3 years
Very complex syntax not achieved until well into the school years
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Are late talking toddlers at risk for specific language
impairment?
Courtesy: D. Thal
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Normal Variability
0
20
40
60
80
100
120
140
160
180
<50 50-100 100-150 150-200 >200
10th percentile
50th percentile
90th percentile
Number of words produced in relation to number of words understood by 12- to 16-month-old children at the 10th, 50th, and 90th percentile on the MacArthur Communicative Development Inventories
Number of words understood
Nu
mb
er o
f w
ord
s p
rod
uce
d
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Variability in normal development
Range of word produced by typically-developing girls on the MacArthur Communicative Development Inventories (Fenson, Dale, Reznick, Thal, Bates, Hartung, Pethick, & Reilly, 1993) 0
100
200
300
400
500
600
700
16mo
18mo
20mo
22mo
24mo
26mo
28mo
30mo
10th
25th
50th
75th
90th
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When to worry (1)
Questionable hearing at any age, including at birth, refer to audiology
No reciprocal eye gaze/dialog at any age No pointing by 1 year No comprehension of speech ≥1 year No turning when called by name ≥15 months < 10 words at 18 mos No 2 word phrases at ≥2 years
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When to worry (2)
Unintelligible to parents at 2 years Unintelligible to strangers at 3 years Language not communicative, e.g.,
talks to no one in particular Abnormal features of speech:
echolalia, scripts, pedantic vocabulary, aberrant prosody (e.g., robotic, singsong), selective mutism
Any loss of language milestones (including communicative gestures)
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Useful clinical language tools
MacArthur Development Communicative Inventories. L. Fenson et al. Paul Brookes, 1993 For kids < 30 months. Infant and verbal toddler versions Parents collect the data on comprehension, production and
use Extremely well standardized in multiple languages
Early Language Milestone Scale. J. Coplan, Pro-Ed 1987, ELM-2 2012 For kids < 3 years. Scored by observer. Quick Format similar to the Denver ELM-2: also for older DLD kids, , uses a kit
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DEVELOPMENTAL LANGUAGE DISORDERS
(DLDs)
a.k.a.
SPECIFIC LANGUAGE DISORDERS (SLIs)
or DYSPHASIAS
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Differential diagnosis of inadequate language development
Hearing loss
Specific language disorder (dysphasia)
Intellectual deficiency
Autism
Selective mutism (recording of normal
speech required!
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2 types of information the child neurologist needs to make a specific behavioral language
diagnosis
The familiar input – processing – output brain pathway
Levels of language encoding
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Steps in language processing
Input Output (sensory) (motor)
Decoding Higher order Encoding processing
Input Output (sensory) (motor)
Decoding Higher order Encoding processing
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Levels of language encoding (1)
Phonology – speech soundsphonetics – segmentalprosody – suprasegmental
Grammarsyntax (word order)morphology (word endings, etc.)
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Levels of language encoding (2)
Semantics – meaning of utteranceslexicon – word dictionary in brainmeaning of connected speech
Pragmatics – conversational languageverbal – turn taking, referencing, etc.nonverbal – facial expression, gestures,
body posture, prosody
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Associated deficits (frequent!)
Oromotor deficits (pseudobulbar palsy, etc.): frequent in dysfluent children with verbal dyspraxia and
those with mixed receptive/expressive disorders but do not “cause” the language disorder
Intellectual deficiency: does not cause specific language disorders
Autism: intellectual deficiency & lack of drive to communicate =
inadequate explanations for the language disorder Selective mutism:
must have recording of allegedly “normal” speech at home
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Types of dysphasia “Pure” expressive (comprehension OK, pragmatics
OK, affects only phonology ± syntax) fluent but phonology very impaired (phonologic programming --
PP) dysfluent or mute (verbal dyspraxia -- VD)
Mixed expressive/receptive (affect phonology + syntax + semantics ± pragmatics) comprehension ≥ expression (phonologic-syntactic or MER) no comprehension = verbal auditory agnosia (verbal auditory
agnosia VAA)
Higher order processing (semantics ± pragmatics) word finding deficit dysfluent, immature syntax (lexical
syntactic -- LS)fluent, verbose, comprehend less than they can say, use
scripts. Most often in Asperger-type children (semantic pragmatic --SP)
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DLD proposed syndromes
SP semantic/pragmatic LS lexical syntactic PP phonologic programming VD verbal dyspraxia MER/PS mixed expressive receptive
or phonologic syntactic VAA verbal auditory agnosia
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Work-up, Prognosis
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Standard Work-up of DLD Preschooler
Physical/neurologic evaluation: syndrome? Family history Formal hearing evaluation unless phonology is 100%
OK Rarely need for EEG, imaging, genetics (several genes
now known) unless for research Refer to speech pathology (and psychology) Refer to preschool (more effective than speech Rx
alone) Follow-up needed: most speak but later problems
likely(see Rutter 1881, Aram, 1984 Beichtman 1996, etc.)
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Potential Outcome Predictors in
Developmental Language Disorders• Gender
• Not ethnicity
• Bilingual exposure?
• Family income
• Parental education
• Ear infections
.
• First degree relatives with history of Learning/reading
disabilitySpeech or language
disordersNeurological disorders
• Use of gestures
• # of words understood
• # of words produced
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Course of language development in DLD/SLI
Classification is not stableMore children move out of or into the category than
remain in it between 3 an 5 years of age (Silva)
Children with delays in comprehension and production are at greater risk for continued “delay” than those with normal comprehension (Bishop, Silva, Tallal)
Younger children at start of intervention tend to have a better prognosis (Bishop, Silva, Tallal)
Donna J. Thal Ph.D.
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Course of development in DLD
5 ½ y. DLD with normal language scores: likely to remain in the normal range on such tests (Bishop)
However, lower phonological processing scores likelyhalf read below age level, at 15 years of
age (Stothard et al., 1998)