sli and the brain

Specific language impairment and the brain

Dorothy V M Bishop

Damage tothese areason the leftside of the brainusually causeslanguage disorder (aphasia)in adults

Specific language impairment (SLI)is sometimes called

“developmental dysphasia” or “developmental aphasia”

But the causes are different from causes of adult acquired aphasia

Evidence against brain damage in children with SLI: 1.

Children who do have brain injury affecting the language areas don’t usually develop SLI

Brain scan after removal of diseased cortex on left side of brain to control epilepsy

Child without left-sided language areas can still learn to talk and understand!

Right side able to take over language functions

Extreme example of language developmentafter early damage to language areas

Evidence against brain damage in children with SLI: 2.

Brain scans don’t usually show evidence of any injury, unless child also has other signs of neurological damage– E.g., epilepsy or motor (movement) problems

severe enough to indicate brain damage

Jernigan, T., Hesselink, J. R., Sowell, E., & Tallal, P. (1991). Cerebral structure on magnetic resonance imaging in language- and learning-impaired children. Archives of Neurology, 48, 539-545.

Early study comparing children with SLIwith a typically-developing control group

Routine examination of MRI structural brain scans:

•No abnormality in 16/20 scans of language-impaired•Slight abnormalities in the other four

•No abnormality in 8/12 typically-developing control children•Slight abnormalities in the other four

Emphasises that we should not over-interpret slight abnormalities – they are common!

“There is now overwhelming evidence that children with [specific] learning disabilities do not have “holes in the brain”. No ..studies have found a one-to-one correlation between behavioural symptoms and MRI or postmortem pathology in [specific] learning disabilities”C. Leonard, 1997, p 161

Because of UK/US differences in terminology, [specific] added for clarification

Leonard, C. M. (1997). Language and the prefrontal cortex. In N. Krasnegor, G. R. Lyon & P. S. Goldman-Rakic (Eds.), Prefrontal cortex: Evolution, development, and behavioral neuroscience (pp. 141-166). Baltimore: Paul H. Brookes.

Growing evidence that genes are important in causing SLI

Genetic influence could affect early stages of brain development

What would this look like?– Brain may be atypical in shape/size?– Connections between brain regions affected?– Microscopic differences in brain cell arrangements?

Not many studies: still early days

Abnormal brain development in SLI?

Malformation evident from brain scans Typically associated with very severe

expressive language difficulties and epilepsy

See blog by Rob Rummel-Hudson who described the long pathway to getting a diagnosis for his daughter, Schuyler http://www.schuylersmonsterblog.com/

Rare cases with malformations affecting language areas: perisylvian polymicrogyria

More commonly, only subtle evidence of developmental abnormality on MRI

Clark, M. M., & Plante, E. (1998). Morphology of the inferior frontal gyrus in developmentally language-disordered adults. Brain and Language, 61, 288-303.

IFS: inferior frontal sulcusAAR: anterior ascending ramusAHR: anterior horizontal ramusPCS: precentral sulcus

Frontal language region (defined in blue) very variable from person to person:Here looked at number of ridges (gyri) and fissures (sulci) in this region

Clark & Plante studyNumber of people with extra sulcus (either side)1. Parents of language-impaired child

Parent with no language problems: 5/10 = 50%Parent also has language problems: 20/30 = 67%

2. Parents of child without language problemsParent has no language problems: 13/34 = 38%Parent also has language problems: 6/8 = 75%

Conclusion: Greater chance of extra sulcus in those with language problems, but association is far from perfect:•Around 1/3 of adults with no language difficulties in self or child have extra sulcus, •Around 1/3 of adults with language difficulies in self AND child don’t have extra sulcus

Subtle brain abnormalities associated with rare gene mutation that cases SLI

Yellow:Affected members of KE family (N = 10) had LESS grey matter than 10 age-matched controls

Yellow:Affected family membershad MORE grey matterthan controls

Watkins, K. E., (2002). MRI analysis of an inherited speech and language disorder: structural brain abnormalities. Brain, 25, 465-478.

Study using structural and functional scanning of children with SLI

• No gross differences seen in the brain

• Subtle differences in language areas in distribution of grey matter – very similar pattern to KE family

• Also did functional brain imaging (fMRI). Can’t record brain activation while speaking, because movements interfere with the recording. But can look at activation of language areas when doing a silent language task:

• Hear a word definition (e.g. “bees make it”) and must think of the word

Badcock, N., Bishop, D., Hardiman, M., Barry, J. G., & Watkins, K. (2011). Co-localisation of abnormal brain structure and function in Specific Language Impairment. Brain and Language, 120(3), 310-320. doi: 10.1016/j.bandl.2011.10.006

fMRI: Activation to Silent Naming

Amount of brain activation in silent naming task for typical children (blue), brothers and sisters of children with SLI (green) and children with SLI (red).

SLI group shows reduced activity in language regions

Badcock, N., Bishop, D., Hardiman, M., Barry, J. G., & Watkins, K. (2011). Co-localisation of abnormal brain structure and function in Specific Language Impairment. Brain and Language, 120(3), 310-320. doi: 10.1016/j.bandl.2011.10.006

Two sides of the brain look similar, but functiondifferently

In most people, the left side is more active during language tasks

Cerebral lateralisation

Adults with history of SLI or autism

typicalN=11

ASD + low languageN = 11

SLI SLIhistory currentN= 9 N = 11

Whitehouse, A. J. O., & Bishop, D. V. M. (2008). Cerebral dominance for language function in adults with specific language impairment or autism. Brain, 131, 3193-3200.

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Study using functional transcranial Doppler ultrasound to measure blood flow to left and right sides of brain while thinking of words starting with a given letter

Adults with history of SLI or autism

typicalN=11

ASD + low languageN = 11

SLI SLIhistory currentN= 9 N = 11

Whitehouse, A. J. O., & Bishop, D. V. M. (2008). Cerebral dominance for language function in adults with specific language impairment or autism. Brain, 131, 3193-3200.

Late

ralit

y in

dex

L biased

R biased

Study using functional transcranial Doppler ultrasound to measure blood flow to left and right sides of brain while thinking of words starting with a given letter

People withlanguagedifficulties tend to be lesslateralised.

We don’t yetknow why thisis so

Overall….. Most children with Specific Language Impairment don’t have

any evidence of brain damage They may have slight differences in the size of different brain

regions, or in the balance of activity on left and right sides The differences are typically small and not seen in all children

with SLI It’s not possible to diagnose SLI from a brain scan Neurological investigations aren’t usually recommended

unless the child has very severe language difficulties, physical impairments (motor problems) or epilepsy

For further readingsee reference list on:

http://www.slideshare.net/RALLICampaign/sli-and-the-brain