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Language Development and the Brain: A Phonological Perspective Usha Goswami Centre for Neuroscience in Education University of Cambridge. How does the Brain encode Speech?. Auditory signal Visual dynamics Encoding via oscillations?. The Brain and the Speech Signal. - PowerPoint PPT Presentation
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Language Development and the Brain:A Phonological Perspective
Usha GoswamiCentre for Neuroscience in EducationUniversity of Cambridge
How does the Brain encode Speech?
-Auditory signal
-Visual dynamics
-Encoding via oscillations?
The Brain and the Speech Signal
Phonetics – ba / da
Syllable structureRhythmProsody
NINE SEVEN TWO THREE TWO
Behavioural Science
Babies use speech rhythm as an early segmentation cue
Can also distinguish e.g. ba / pa, syllable stress
What is happening in the Brain?Envelope and Fine Structure
Smith, Oxenham & Delgutte, 2002: Auditory Chimera
Method for contrasting envelope (slowly varying) and fine structure (rapidly varying) componentsof speech (or other sounds) experimentally
CHIMERA = Envelope cues from one sentenceFine structure cues from another sentence
Which sentence will listeners hear?
Auditory Chimera Sentences
Perception mainly from fine structureNot much from envelope
Perception mainly from envelopeNot much from fine structure
Envelope information mostimportant for speech intelligibility
Early language acquisition:critical role for envelope?
Envelope information mostimportant for speech intelligibility
Emphasises importance of speechrhythm and syllable structure
Envelope: Importance of Rise Times
Spectro-temporal profile (STeP)
Spectrogram + Waveform
Spectro-Temporal Profile (STeP) Spectrogram+Waveform
Greenberg et al. (2003)
Combination of Cues Important“SEVEN”
Amplitude Envelope and Stressed Syllables
[s]
[eh]
[vx]
[en]
juncture accented syllable
unaccented syllable
“Seven”
mean duration
Full-spectrumperspective
Greenberg 2002
[s] [eh] [vx] [en]
Rise times
How Does the Brain Encode Modulation?
Language Representations
Neurons
Networks
Neuroscience
Simple neural codingmechanisms, likeoscillation at different rhythmic rates, appearto be critical.
Delta: 0.5 – 4 HzTheta: 4 – 8 HzGamma: 20 – 50 Hz
Speech signal
Rapid modulationsGamma networks
20 – 50 Hz
Slow modulationsTheta networks
4 – 8 Hz
Binding forspeech perception
The Brain Samples Information in DifferentFrequency Bands (Theta, Gamma ..)
“syllables”“phonemes”
Speech signal
Rapid modulationsGamma networks
20 – 50 Hz
Slow modulationsTheta networks
4 – 8 Hz
Speech percept
Phonetics:ba - pa
RhythmSyllablesMeter
Rise Times Enable Phase Locking?
Hickok, Poeppel
Alignment with“edges” in signal
2 Hz
10 Hz
Hamalainen, Rupp et al. – Phase Locking
Speech signal
Rapid modulationsGamma networks
20 – 50 Hz
Slow modulationsTheta networks
4 – 8 Hz
Speech percept
Phoneticsba - pa
RhythmSyllablesMeter
Early language experiences entrain the oscillators?
Infant-directed speech
Perceptual magnets
Implications for Language Development Prior to Schooling
Entraining the oscillators – activities that emphasise rhythms and metrical structure of speech
- nursery rhymes- poetry- music and singing- other rhythmic experience – dancing
marchingplaying instruments
Link To Phonology:Word Representations in the Brain
semantic representation
phonologicalrepresentation
motorprogramme
Contribution of Brain Imaging
Brain(mental lexicon)
Phonology
Acousticsignal
How does the phonological system develop?
Need to understand how basic auditory processingand learning to talk contribute to the development ofwell-specified phonological representations
Phonological Representation
What are the Brain Representations of Language like Prior to Reading?
semantic representation
phonologicalrepresentation
motorprogramme
The Mental Lexicon
Age 1 year produce 50 – 100 words
Age 6 years produce 6000 wordscomprehend 14,000 words
Developmentally, requires fine-grained representations of similarities and differences in sound
Spoken Language Processing
Lexicon
Acoustics
PhoneticsPhonology
Spoken Language Processing
Lexicon/Reading
Acoustics
PhoneticsPhonology
Bottom-Up
Spoken Language Processing
Lexicon
Acoustics
PhoneticsPhonology
Top-down
The Development of Phonological Awareness
Children gradually become “aware” of soundunits within words as they develop theirlanguage skills
A universal developmental sequence is found acrosslanguages
Levels of Phonological Awareness
Syllable (butterfly, wigwam, soap)
Rhyme (onset-rime: str - eet, fl - eet)
Phoneme (smallest units of sound that change meaning: cat-pat, cat-cot, cat-cap
but pin … spoon)
Basic Unit of Speech Processing – The Syllable
g r
gr
a s p
asp
graspsyllable
onset rime
phonemes
(develop largely via reading)
The Development of Phonological Awareness
Oddity Task: Bradley & Bryant, 1983
Alliteration: hill, pig, pin
Rhyme 1: cot, hat, pot
Rhyme 2: sit, pin, win
Oddity Task: English, German, Chinese
0
20
40
60
80
English German Chinese
% c
orr
ec
t
onset rime
Oddity Task: Dyslexic Children
(Bradley & Bryant, 1978)
0
20
40
60
80
100
Allit Rhyme1 Rhyme2
%c
orr
ec
t
Dys RL
Gains in Reading and Spelling after 2 yrs,Adjusting for Age and I.Q.
60
80
100
Read Acc ReadComp
SpellAd
just
ed s
tan
d s
core
in m
on
ths Train Ctrl1 Ctrl2
Predicting Reading Acquisition
BrainLanguage
Reading
Phonology
Language playNursery rhymes
“AuditoryOrganization”
Phonological& orthographicconnections
Measuring Syllable and Phoneme Awareness
e.g., tapping out sounds using a drumstickcounting out sounds using plastic tokens
Syllable level
popsicle 3 tapsbutter 2 tapssoap 1 tap
Phoneme level
book 3 tapsup 2 tapsI 1 tap
Counting Tasks: Syllable vs Phoneme
0
20
40
60
80
100
Nor Ger Fre Tur Gr
% c
orr
ec
t
phoneme syllable
Rate of Phonemic Development
Languages vary in the degree to which letters have a 1:1mapping to sound
GreekFinnishGermanItalianSpanish
SwedishDutchIcelandicNorwegian
FrenchPortugueseDanish
English
Phoneme counting at end of Grade 1
% correct
Greek (Porpodas) 100Italian (Cossu et al.) 97Turkish (Durgunoglu & Oney) 94German (Wimmer et al.) 92Norwegian (Hoien et al.) 83French (Demont & Gombert) 61English (Perfetti et al.: Grade 2) 65
Predicting Reading AcquisitionAcross Languages
BrainLanguage
Reading
Phonology SyllablesRhymesPhonemes
The Development of Phonological Representations
Infancy
- physical changes in signal where languages placephonetic boundaries
- statistical learning of prototypes and phonotactics
- use of prosodic cues to segment syllables and words
Within first year have proto-lexical representationsthat encode stress and segmental information
The Development of Phonological Representations
Early Childhood
- enormous increase in vocabulary
- pressure for segmental specificity
- syllable structure varies across languages
- phonological “neighbourhood density” variesacross languages
PHONOLOGICALREPRESENTATIONS
OF WORDS
Vocabulary size andrate of expansion
Speech processingskills (input and
output)Rhythmic cues Phonological
neighbourhooddensity
(language specific)
Linguistic factorseg, sonority profile(language specific)
Word frequency/familiarity/
ageof acquisition
Speech-readingeg, lip shape
Syllable Structure(languagespecific)
How Reading Changes the Brain
PHONOLOGICALREPRESENTATIONS
OF WORDSchair tray tip
Vocabulary size andrate of expansion
Speech processingskills (input and
output)Rhythmic cues? Phonological
neighbourhooddensity
(language specific)
Linguistic factorseg, sonority profile(language specific)
Word frequency/familiarity/
ageof acquisition
Speech-readingeg, lip shape
Reading and spelling acquisition
(phoneme level)
Syllablestructure(language Specific)
Development of Phonological Awareness: Language Universal?
Preschool: large units
syllablesrhymes
With schooling: small units
phonemes
English Monosyllables: Approx. 4000
CV sea 5%
CVC cat 43%
CVCC desk 21%
CCVC trip 15%
CCVCC grasp 6%
German: 1400 French: 2500
Representing Phonemes Varies Across Languages
GreekFinnishGermanItalianSpanish
SwedishDutchIcelandicNorwegian
FrenchPortugueseDanish
English
Languages vary in the degree to which letters have a 1:1 mapping to sound, and this affects how rapidly phonology gets “re-mapped” in the brain
EU Study: Word and Nonword Reading (cvc)
0
20
40
60
80
100
Gk Fin Ger It Sp Sw Du Ic N Fr Po Da Eng
% c
orr
ect
NW "vuf" Word "cup"
Rates of development largely explained by spelling transparency across languages
E.g., ‘a’
German English
Hand hand
Ball ball
Garten garden
Rates of Development across Languages
- development of phonemic representation slower in less consistent orthographies
- development of grapheme-phoneme recoding skills(“sine qua non” of reading acquisition) alsoslower in less consistent orthographies
Educational Neuroscience
Importance of understanding how the brain encodes information
Importance of understanding how environment shapes the basic encoding
Focus on causal mechanisms of development
Deeper understanding of development
Implications for Language Development Prior to Schooling
Need to hear as much language as possible
Importance of “rich” language
Rich language enhanced in story reading interactions
Entraining the oscillators – activities that emphasise rhythms and metrical structure of speech
- nursery rhymes- poetry- music and singing