Brain Abnormalities in Language Disorders and in Autism

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It has been speculated that autism and specific language impairment share common underlying neural substrates because of the overlap in language impairment issues and evidence suggesting parallels in other domains and implying a possible shared genetic risk. Anatomically the two sets of disorders have generally been studied using different methodologies, but when identical methodologies have been used substantial similarities have been noted. Functionally there is a growing body of literature suggesting sensory perception abnormalities that have parallels in both conditions and that may be upstream of language abnormalities. Finding upstream mechanisms that impact language and non-language abnormalities in autism and specific language impairment would impact the orientation taken by translational attempts to use science to design treatments.

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Asymmetry

The populational predominance of leftward lateralization of language functions has made the study of asymmetry attractive in autism and SLI, because it is known that there is a higher frequency of ambidextrousness, left-handedness, or right hemisphere language dominance in individuals who have language disorders and autism. This question has been pursued in imaging studies of autism and SLI subjects, but it has been addressed differently in the two groups. We address large-scale, local, and

Sensory perception deficits in autism

Autism has been linked with impairments in simple sensory perception early in the hierarchy of cortical processing, in the visual [76], [77], [78], [79], [80], [81] and auditory [82], [83], [84], [85], [86], [87], [88] domains, and to some extent also in the somatosensory domain [89], although those data are so far mostly anecdotal. To date, the correlation between these sensory impairments and the behavioral characteristics of autism remains unknown. More specifically, the extent to which some

Neuropathology and pathophysiologic considerations

Moving down from macroanatomy to tissue rather than up to function in the biologic hierarchy leads to neuropathology and cellular and molecular pathophysiology. There is a modest amount of neuropathologic literature in autism, almost none in SLI, and some in dyslexia. Findings in dyslexia have included ectopia, altered asymmetries, abnormal minicolumns [116], and abnormalities in the magnocellular system. Animal models developed to pursue some of these findings show an association between

Summary

We have reviewed local and widespread anatomic changes in SLI and autism, and substantial but not complete similarities between the two disorders, and we have reported suggestive sensory processing abnormalities across domains. The findings we have reported go substantially beyond the structural and functional domains that would be uniquely altered if these disorders were based on genes or pathophysiologic processes that specifically targeted the neural substrates of language processing. They

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    This work was supported by NS48455 from NINDS, the Cure Autism Now Foundation, and the Bernard Fund for Autism Research.

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