Language, Reading and Dyslexia

Brain, Mind and Education

Outline of the Session

• Spoken language

• Written language? – Studies of the normal reading process

• Brain differences in ‘atypical readers’

• What causes dyslexia?

The brain basis of spoken language

Is spoken language innate?

• There is much debate about how innate e.g. – nativists such as Chomsky, Pinker (evolutionary instinct) – versus connectionists/neuroconstructivists say “experiences specialise us”

• Language in babies? Dehaene & Dehaene-Lambertz (2006) scanned 3 month old babies while they were listening to speech (asleep!). – Activation was found in regions associated with language

(e.g. Broca’s area and superior temporal regions) – similar language areas to adults

The brain basis of spoken language

• Babies come into the world able to distinguish between all speech sounds.

• Some of this ability is lost by 6 months – the child can only distinguish sounds he/she has been exposed to. The brain does not seem to treat the differences as ‘significant’ and behaviourally, we do not experience the differences –a sensitive language window. (Kuhl et al., 1992)

Speech – 2 classic regions (Broca’s and Wernicke’s)

• We have known for a long time that spoken language appears to be handled by the left-hemisphere of the brain - in most people.

• Paul Broca, a C19th neuoanatomist first linked speech difficulties to damage to the inferior frontal gyrus (IFG) of the L-hemisphere (case of ‘Tan’) – Broca’s area.

• Damage to this area can cause dysfluent speech

Broca’s Area is near relevant motor cortex

Author: OpenStax College, Creative Commons Attribution 3.0 Unported license.

Primary Motor Cortex (BA 4)

© Was a bee / Wikimedia Commons /  CC-BY-SA 2.1 

Speech & understanding

• A little later, a German neurologist, Carl Wernike, studied brain-damaged patients who could speak but not understand language.

• Damage to the posterior region (Wernicke’s area) of the (left) superior temporal gyrus can result in fluent language that is meaningless.

© Dryke. GNU Free ocumentation License, Version 1.2 or any later version published by the Free Software Foundation;

Wernicke’s Area is near auditory cortex

Primary Auditory Cortex (BA 41,42)

Modern imaging techniques show a much wider range of regions involved with producing meaningful speech:

(Poeppel et al, 2008)

Parieto-temporal (left)Auditory-Motor mapping Sensori-motor input/output links

Inferior Frontal Gyrus (left)Articulatory Speech Codes(speech movements)

Middle Temporal GyrusInferior Temporal Gyrus (left)Sound-meaning, lexical activation(Identifying a word and its meaning)

Superior Temporal Gyrus (bilateral)Acoustic-phonetic mapping = “t” links to sound of “t”

Speech

Reading – studies of normal readers

• Until quite recently, no brain data on ‘normal’ reading acquisition process.

• Scanning children now possible, using fMRI techniques (see also EEG).

• Turkeltaub et al. (2003) have begun to look at the brain activity of children of different ages during a reading task.

Some terms…

• Grapheme – unit in a written language – e.g. alphabet

• Orthography – spelling

• Phoneme – unit in spoken language

• Lexicon – whole set/list of units (orthographic, phonological, etc)

Dual-route model of reading wordsColtheart (2001)

Direct – supposedly more used by skilled readers

Indirect – phonologically mediated access – supposedly slower

But…..

• Phonological processing appears very rapid – as demonstrated by studies of parafoveal* preview – in which attention momentarily shifts to phonological information later in sentence (Polletsek et al. 1992)

• And….this is also true for skilled readers (see also Ashby refs below)

* Parafoveal vision = off centre but not quite peripheral

-> Triangle model of reading- from connectionists – artificial neural networks

Phonological Processor

Semantic Processor

Orthographic Processor

Orthographic processingPhonological processingSemantic processing

So reading systems are distributed, and contain redundancyDiagram interpreted from Ashby(2012)

Visual word form area

Reading Wernicke’s/angular gyrus

Networks for reading are closely related to those for speech

Studies of the normal reading process (Turkeltaub et al., 2003)

• 41 participants (6-22 years).• Carried out a feature detection (implicit word

processing) task in the scanner:– Shown a series of words and false font strings– Press the button in right hand if stimulus has an

ascender (tall letter), left hand if not

sauce alarm

“no” “yes”

↩⊸ ⊋≀≻ ∿∿⌠∿∿

Studies of the normal reading process

• This procedure controls for brain processes not specific to decoding processes (e.g. spatial processing, motor planning).

• When the activity associated with words was compared with that for the false font strings, the areas of brain activation that were specific to words were:– Left posterior temporal cortex – Left inferior frontal cortex – Right inferior parietal cortex

Studies of the normal reading process

• Reading ability also measured, to study brain activity in relation to reading level.

• Measures of phonological skills were also taken:– Phonological WM (digit span)– Phonological awareness– Phonological naming (RAN)

Studies of the normal reading process

Findings indicate that:• Temporoparietal cortex activity (including the left

superior temporal sulcus, Wernicke’s area - see above) matures early and continues to be involved in reading throughout adulthood.

• Superior temporal sulcus is implicated in cross-modal integration (e.g. mapping print to sound) - early predictor of reading outcome?

• This area was correlated with phonological awareness skill.

“a left region” linked to reading/phonological skills

Left temporal language area – “visual word form area”

Contralateral to left temporal language area – non-phonological memory – used by dyslexics

Posterior Fusiform Non-lexical (i.e. not words) visual pattern recognition

LEFT RIGHT

Interpretation of (Turkeltaub et al., 2003)

Studies of the normal reading process

• Findings indicate:• A progressive disengagement of right visual cortex

over the course of reading acquisition.• Supports a behavioural model of moving from relying

more on visual features of each letter (right fusiform), to a phoneme-grapheme stage (left IFG), then lexical processing (visual word form area) – i.e. whole words & using known whole words to identify new ones.

Logographicstage

Alphabeticstage

Orthographicstage

Studies of the normal reading process

Weird but true: Turkeltaub et al.’s study provides support for ideas about reading that were proposed in 1925 by the American neurologist Samuel Orton….

Orton suggested that, in the course of learning to read, children need disengage posterior RH visual representations that interfere with proper word identification.

Studies of the normal reading process in different languages

• Different languages engage the brain areas differentially depending on the regularity of the orthography (e.g. Italian vs. English) – Paulesu et al. (2001)

• Regular languages rely more on the middle parts of the brain, while irregular languages use the area at the back of the brain to a greater extent – why might this be?

• Individuals with dyslexia• The study of differences in the brains of

individuals with dyslexia has a long history (e.g. Orton)

• However, it is still a very contentious area of research

Brain differences in ‘atypical readers’

Brain differences in ‘atypical readers’

Individuals with dyslexia (see Beaton (2005) Pugh (2001), Shaywitz (2001))

• Brain differences have been found in, for example:• Activity in the language areas of the left hemisphere

(reduced) and in the right hemisphere (increased).• Reduced activity in the left insular region (a bridge between

the different language processing areas).• Left Planum temporale (the superior temporal gyrus) larger

(i.e. PT is symmetrical).• Differences in the corpus callosum.• Reduced activation in the cerebellum.• Magnocellular system deficits (Visual motion sensed by special set of visual nerve

cells: magnocellular system that controls visual attention and eye movements - system responsible for timing visual events when reading, auditory magnocellular system would influence phonological acqusition)

Causes of Dyslexia

• Biological differences cited above• For some recent biological theories see

Beaton, A.A. (2005)• These theories include:

– Phonological delay/deficit– Temporal (time) processing– Visual problems

Causal Modelling – how should we think about ‘cause’?

• Brain

• Mind

• Behaviour

Model 1

Phonological

Delay/deficit

e.g. Clay 1987"You have hissed all my mystery lectures and tasted a whole worm.”

Genetic difference

Brain difference

Phonological processing deficit

Grapheme-phoneme system not learner

English orthography

Spoonerisms difficult

Phonological tasks difficult

Problems with naming

Learning to read difficult

brain

cognition

behaviourEN

VIR

ON

ME

NT

Model 2

Temporal Processing

Tallal et al. (1997)

English orthography

Magnocellular abnormality

Slow temporal processing

Auditory deficit

Poor speech development

Visual deficit

Poor motion detection

Poor tone discrimination

brain

cognition

behaviour

EN

VIR

ON

ME

NT

Phonological processing problems

Learning to read difficult

Grapheme-phoneme system not learned

Spoonerisms difficultPhonological

tasks difficult

Problems with naming

Model 3

Skill Automization

Nicholson and Fawcett (1990)

English orthography Phonological

processing problems

Learning to read difficult

Grapheme-phoneme system not learned

Spoonerisms difficultPhonological

tasks difficult

Problems with naming

brain

cognition

behaviour

Genetic difference

cerebellum difference

Speech motor areas

Poor skill automization

timing

fine manual dexterity Time

estimation

Balance problems

EN

VIR

ON

ME

NT

Model 4

Visual Damage

e.g. Stein (’94) – problems with binocular vision convergence

No phonological processing problems

Learning to read difficult

Grapheme-phoneme system not learned

Spoonerisms not difficultPhonological

tasks not difficult

No problems with naming

brain

cognition

behaviour

EN

VIR

ON

ME

NT

Genetic difference

Specific damage to visual system

Visual performance problems

Interventions for education

• Does any of this knowledge have implications for education?

• Possibly….

• A number of interventions have been developed which map onto the neurological evidence related to reading and reading disorders

Fast ForWord

• An intervention aimed at remediating impairments in the temporal processing deficits (found in children with speech and reading problems).

...software adapts to individual skill levels and responses, adjusting the learner's content exposure and targeting correct responses approximately 80% of the time, which maintains challenge and motivates success.

                                                 ....Develops memory, attention, processing and sequencing, the underlying cognitive processes required for reading and learning. ....learning techniques based on decades of neuroscience research. ...to get results in as little as 3-6 weeks! (...30 minutes each day, five days a week, for 3 - 6 weeks )

Does it work?

• Evidence for behavioural and neural remediation (e.g. Temple et al. 2003)

• A lot of initial enthusiasm but negative reviews are beginning to come through too (e.g. Borman (2009)

Dyslexic children increased activation in areas ringed in red

Other interventions have also remediated reading and brain activity

• Phonologically-targeted training (Eden et al., 2004): Dyslexic adults were given a programme of training involving: “sound awareness, establishment of the rules for letter-sound organisation, sensory stimulation, and articulatory feedback” The trained group showed improvements at the behavioural level, plus changes (increases) in task-related brain activity (left hemisphere parietal cortex and some RH regions)

• See also Shaywitz(2004) for more remediation of reading difficulties and their neural correlates

Will brain imaging become part of technology design?

•Graphogame is a non-commercial system developed at the University of Jyväskylä (Finland)

•Introduces association of graphemes and phonemes according to frequency and consistency of grapheme in a given language

•Onine algorithms analyze a child’s performance and rewrite the lesson plans “on the fly” depending on which specific confusions the learner shows

Brem et al. (2010)

• fMRI and EEG together (spatial and temporal resolution):– practise with the game initiates print-sensitive

activation in a critical component of the mature reading network located in the left occipitotemporal cortex - “visual word-form”.

– If this occipito-temporal print sensitivity established during the earliest reading acquisition, suggests crucial later reading network first adopts a role in print:sound mapping.

– Such results provide insight into how the software succeeds in supporting literacy, how/when it should be implemented and how neuroscience can be used to inform TEL design.

Brem, S., S. Bach, et al. (2010). "Brain sensitivity to print emerges when children learn letter-speech sound correspondences." Proceedings of the National Academy of Sciences of the United States of America 107(17): 7939-7944.

…and does dyslexia exist anyway?!

Prof. Julian Elliot (Durham):

1. Is dyslexia a clinically or educationally meaningful term for differentiating between children with reading difficulties?

2. To what extent would the dyslexic diagnosis guide the educator in devising appropriate forms of intervention?

3. To what extent should the dyslexic diagnosis result in the differential allocation of resources or other forms of special arrangement?

Elliott, J. G., & Gibbs, S. (2008). Does dyslexia exist? Journal of Philosophy of Education, 42(3-4), 475-491.