Specific language impairment and the brain Dorothy V M Bishop
Damage tothese areason the leftside of thebrainusuallycauseslanguagedisorder(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 affectingthe language areas don’t usually develop SLI
Extreme example of language development after early damage to language areas 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
Evidence against brain damage in children with SLI: 2.Brain scans don’t usually show evidence ofany injury, unless child also has other signs ofneurological damage– E.g., epilepsy or motor (movement) problems severe enough to indicate brain damage
Early study comparing children with SLI with 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!Jernigan, T., Hesselink, J. R., Sowell, E., & Tallal, P. (1991). Cerebral structure onmagnetic resonance imaging in language- and learning-impaired children. Archives ofNeurology, 48, 539-545.
“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 clarificationLeonard, C. M. (1997). Language and the prefrontal cortex. In N. Krasnegor, G. R. Lyon& P. S. Goldman-Rakic (Eds.), Prefrontal cortex: Evolution, development, and behavioralneuroscience (pp. 141-166). Baltimore: Paul H. Brookes.
Abnormal brain development in SLI? 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
Rare cases with malformations affectinglanguage areas: perisylvian polymicrogyria 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/
More commonly, only subtle evidence of developmental abnormality on MRI Frontal language region (defined in blue) very variable from person to person: Here looked at number of ridges (gyri) and fissures (sulci) in this IFS: inferior frontal sulcus region AAR: anterior ascending ramus AHR: anterior horizontal ramus PCS: precentral sulcusClark, M. M., & Plante, E. (1998). Morphology of the inferior frontal gyrus indevelopmentally language-disordered adults. Brain and Language, 61, 288-303.
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 problems Parent 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 extrasulcus,•Around 1/3 of adults with language difficulies in self AND child don’t haveextra 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 members had MORE grey matter than controlsWatkins, 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 wordBadcock, 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 regionsBadcock, 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
Cerebral lateralisationTwo sides of thebrain look similar,but functiondifferentlyIn most people, theleft side is moreactive duringlanguage tasks
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 Laterality index L biased R biased typical ASD + low SLI SLI N=11 language history current N = 11 N= 9 N = 11Whitehouse, A. J. O., & Bishop, D. V. M. (2008). Cerebral dominance for languagefunction in adults with specific language impairment or autism. Brain, 131, 3193-3200.
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 People with Laterality index L biased language difficulties tend to be less lateralised. R biased We don’t yet know why this typical ASD + low SLI SLI is so N=11 language history current N = 11 N= 9 N = 11Whitehouse, A. J. O., & Bishop, D. V. M. (2008). Cerebral dominance for languagefunction in adults with specific language impairment or autism. Brain, 131, 3193-3200.
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