SLI and the brain
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Transcript of 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.
Late
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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
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