Language, its development and

pathologiesIsabelle 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 Output (sensory) (motor)

Decoding Higher order Encoding processing

Input Output (sensory) (motor)

Decoding Higher order Encoding processing

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 Map sound to articulation

Ventral stream 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

Hickok 2009

1 2.

3..

3.

4.

4.

5.

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

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 RightVigneau 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, 2013Battaglia 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

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

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

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 Output (sensory) (motor)

Decoding Higher order Encoding processing

Input Output (sensory) (motor)

Decoding Higher order Encoding processing

Levels of language encoding (1)

Phonology – speech soundsphonetics – segmentalprosody – suprasegmental

Grammarsyntax (word order)morphology (word endings, etc.)

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

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 (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)

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

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

disabilitySpeech or language

disordersNeurological disorders

• Use of gestures

• # of words understood

• # of words produced

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.

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)