Brain Advance Access originally published online on October 25, 2008
Brain 2008 131(12):3193-3200; doi:10.1093/brain/awn266
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Cerebral dominance for language function in adults with specific language impairment or autism
Department of Experimental Psychology, University of Oxford, Oxford, UK
Correspondence to: Andrew Whitehouse, Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK E-mail: andrew.whitehouse{at}psy.ox.ac.uk
A link between developmental language disorders and atypical cerebral lateralization has been postulated since the 1920s, but evidence has been indirect and inconsistent. The current study investigated this proposal using functional transcranial Doppler ultrasonography (fTCD), which assesses blood flow through the middle cerebral arteries serving the left and right cerebral hemispheres. A group of young adults with specific language impairment (SLI; n = 11) were recruited along with three comparison groups: (i) adults with a history of childhood SLI, but who did not meet criteria for language impairment in adulthood (SLI-history; n = 9); (ii) adults with an autism spectrum disorder and a comorbid language impairment (ASD; n = 11) and (iii) adults with no history of developmental disorder (typical; n = 11). There was no difference between the chronological age of the four groups, and the SLI and typical groups were individually matched on gender and handedness. During fTCD measurement, participants were asked to silently generate words starting with a given letter and then later required to verbalize these. All of the participants in the SLI-history group and the majority of participants in the ASD (81.8%) and typical (90.9%) groups had greater activation in the left compared to the right middle cerebral arteries, indicating left hemisphere dominance. In contrast, the majority of participants in the SLI groups had language function lateralized to the right hemisphere (54.5%) or dispersed bilaterally (27.3%). These findings suggest that atypical cerebral dominance is not implicated in all cases of poor language development (i.e. ASD and SLI-history groups), but may act as a biological marker of persisting SLI.
Key Words: specific language impairment; autism; cerebral lateralization; language; functional transcranial Doppler ultrasonography
Abbreviations: ASD, autism spectrum disorders; fTCD, functional transcranial Doppler; MCA, middle cerebral artery; SLI, specific language impairment
Received July 2, 2008. Revised August 29, 2008. Accepted September 19, 2008.
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