Over the past 10 years there have been several studies comparing patterns of language impairment observed in individuals who meet criteria for an Autism Spectrum Disorder (ASD) and those meeting criteria for Specific Language Impairment (SLI). While ASD may include individuals who have significant dysfunction in communication, social interactions, and repetitive and restrictive behaviors, SLI refers to individuals who have no other obvious behavioral, cognitive or neurological issues other than deficient language. From a genetic standpoint it has been postulated that perhaps these two disorders share partial genetic etiology. The approach has been to compare language functioning in subjects with SLI with subgroups of subjects with autism in the areas of semantics, syntax, and phonological short-term memory. Conflicting results have been reported. The New Jersey Language and Autism Genetics Study (NJLAGS) is studying families who have at least one individual with a diagnosis of Autism and at least one other individual with SLI, with the goal of identifying language phenotypes to serve as behavioral biomarkers for linkage and association studies.
The object of this study is to examine specific language constructs in family members who meet criteria for language-learning impairment, and compare their patterns of language abilities to those family members who meet criteria for ASD. This study is unique in that not only are the segmental aspects of oral language examined, but reading and higher order language constructs (i.e. abstraction, inference, idiomatic language) are compared between the two groups.
All individuals (including the ASD probands able to receive the measures) received a comprehensive neuropsychological battery including several standardized measures of oral and written language. Language measures included vocabulary, language structure, phonology, verbal short term memory, higher order oral language and reading measures. Individual family members were categorized in terms of language impairment (LI) and reading impairments (RI) based upon their scores on each respective assessment. ASD probands were compared to other sample individuals (LI, RI, and unaffected). Additionally, each family contributed a blood or saliva sample for genetic analyses.
When compared to the entire sample, ASD probands had significantly lower scores on all assessments except for a phonological awareness task. In comparison to those affected for LI, ASD probands scored significantly higher on phonological tasks, reading assessments and Ambiguous Sentences, a higher order language tests. The ASD probands did not have significantly different scores for vocabulary and other higher order language assessments. However, when compared to those affected for RI, ASD probands scored significantly lower on higher order language tests and vocabulary with no significant differences in phonological and reading measures. Similar results were observed when ASD probands were compared to individuals affected for both LI and RI.
Although previous research has been divided as to whether there is sufficient language evidence of shared genetic etiology among individuals with language disorders and individuals with ASD, this study suggests that in addition to segmental language constructs such as structure and phonology, shared language behaviors might occur on the suprasegmental level and will be investigated further.
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