Developmental Language Disorder (DLD; previously SLI)
SPecific language impairment
In collaboration with OSCCI, we are studying families where at least one child has a diagnosis of specific language impairment (SLI). SLI encompasses deficits in the use of language in an otherwise normally developing child and it affects approximately 7% of the English speaking population. Children with SLI have difficulties producing and understanding language for no obvious reason so that a general cognitive impairment, physical abnormality of the speech apparatus, autistic disorder, acquired brain damage or hearing loss cannot account for the language impairments.
Brain structure and function in SLI
We examine and compare brain structure and function during language and auditory processing in these families. We hope to obtain useful insight into neural differences that may underlie these language impairments. So far our imaging work showed overlapping structural and functional abnormalities in children with SLI compared to their unaffected siblings and a group of children showing typical development (Badcock et al., 2011). The amount of grey matter in an area of the frontal lobe (Broca's area), which is involved in speech production, was increased in SLI. But the same area did not show as much activity during a task requiring words to be retrieved from short definition e.g., "bees make it" (=> honey). In the temporal lobes, which are important for comprehending speech and language, we found both reduced amounts of grey matter and reduced activity in SLI.
Based on these findings we have designed a new study investigating neural mechanisms underlying the perception of non-speech acoustic stimuli (pure tones) in these families. We are looking for atypical lateralisation effects in brain areas involved in auditory processing that are associated with impaired language development. Analysing data obtained from both functional and diffusion tensor imaging enables us to investigate trajectories between affected brain regions, so that a better picture of brain abnormalities associated with SLI can be established.
This contribution to our understanding of the neurobiological phenotype will not only aid genetic analyses, but also help to shed light on possible causes of SLI.
Badcock, N. A., Bishop, D. V. M., Hardiman, M. J., Barry, J. G., & Watkins, K. E. (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
Jamison, H. L., Watkins, K. E., Bishop, D. V. M., & Matthews, P. M. (2006). Hemispheric specialization for processing auditory nonspeech stimuli. Cerebral Cortex, 16(9), 1266–75. doi:10.1093/cercor/bhj068