Language, its development
and pathologies
Isabelle Rapin
Pediatric Neurology Seminar, Dec. 4, 2013
No conflict of interest
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
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.
Language in the brain
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
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.
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)
Steps in language processing
Input
(sensory)
Decoding
Output
(motor)
Higher order
processing
Encoding
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
Classic view: Language areas in the
left hemisphere
Classic view: Language
connectivity: left hemisphere
Peoppel et al., 2012
Current view of language in the left
hemisphere
Dorsal
stream
Dorsal stream
Ventral stream
Map sound to
articulation
Map sound to meaning
Gow 2012
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)
Schematic of language processing:
current view
4.
3.
.
1
2.
5.
3.
4.
Hickok 2009
Functional language processing:
dorsal and ventral streams
ATI
A
BA
Ant.temporal lobe
PM
Premotor cortex
Broca area
SMG
Supramarginal gyrus
AUD
Auditory cortex
Spt
Syvian parietal (Left only
STG
Superior temporal gyrus
MTG/ITG Middle/inferior temporal gyrus
Hickok 2009
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
Lateralization of phonologic tasks
(meta-analysis of neuroimaging studies)
Left
Right
Vigneau et al., 2011
Lateralization of lexical semantic
tasks
(meta-analysis of neuroimaging studies)
Left
Right
Vigneau et al., 2011
Lateralization of syntax, sentences
(meta-analysis of neuroimaging studies)
Vigneau et al., 2011
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, 2013
Battaglia et al., Neurosci. Biobehav. Rev. 2012
Language development
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
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
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
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
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
Are late talking toddlers at risk for
specific language impairment?
Courtesy: D. Thal
Normal Variability
 Number of words
produced in
relation to number
of words
understood by 12to 16-month-old
children at the
10th, 50th, and
90th percentile on
the MacArthur
Communicative
Development
Inventories
180
10th percentile
50th percentile
90th percentile
160
140
120
100
80
60
40
20
0
<50
50-100 100-150 150-200
Number of words understood
>200
Variability in normal development

Range of word
produced by typicallydeveloping girls on the
MacArthur
Communicative
Development
Inventories (Fenson,
Dale, Reznick, Thal,
Bates, Hartung,
Pethick, & Reilly, 1993)
700
600
500
400
300
10th
25th
50th
75th
90th
200
100
0
16 18 20 22 24 26 28 30
mo mo mo mo mo mo mo mo
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
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)
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
DEVELOPMENTAL LANGUAGE
DISORDERS (DLDs)
a.k.a.
SPECIFIC LANGUAGE DISORDERS (SLIs)
or DYSPHASIAS
Differential diagnosis of inadequate
language development





Hearing loss
Specific language disorder (dysphasia)
Intellectual deficiency
Autism
Selective mutism (recording of normal speech
required!
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
Steps in language processing
Input
(sensory)
Decoding
Output
(motor)
Higher order
processing
Encoding
Levels of language encoding (1)
 Phonology – speech sounds
 phonetics – segmental
 prosody – suprasegmental
 Grammar
 syntax (word order)
 morphology (word endings, etc.)
Levels of language encoding (2)
 Semantics – meaning of utterances
 lexicon – word dictionary in brain
 meaning of connected speech
 Pragmatics – conversational language
 verbal – turn taking, referencing, etc.
 nonverbal – facial expression, gestures, body
posture, prosody
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
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
syntax + semantics ± pragmatics)
(affect phonology +
 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
LS)
(lexical syntactic --
 fluent, verbose, comprehend less than they can say, use scripts.
Most often in Asperger-type children (semantic pragmatic --SP)
DLD proposed syndromes
 SP
 LS
 PP
 VD
 MER/PS
 VAA
semantic/pragmatic
lexical syntactic
phonologic programming
verbal dyspraxia
mixed expressive receptive or
phonologic syntactic
verbal auditory agnosia
Work-up, Prognosis
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.)
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
disability
 Speech or language
disorders
 Neurological disorders
• Use of gestures
• # of words understood
• # of words produced
Course of language
development in DLD/SLI

Classification is not stable
More 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.
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 likely
 half read below age level, at 15 years of age
(Stothard et al., 1998)
Descargar

Slide 1