Differential language markers of pathology in Autism, Pervasive Developmental Disorder Not Otherwise Specified and Specific Language Impairment

Language impairment is a common core feature in Pervasive Developmental Disorders (PDD) and Specific Language Impairment (SLI). Many studies have tried to define the specific language profiles of these disorders, some claiming the existence of overlaps, and others conceiving of them as separate categories. Fewer have sought to determine whether and how PDD-NOS language profile, including prosody, differs from those of Autistic Disorder (AD) and SLI. Here, 12 children with AD (mean age 9.75; sd 3.5), 10 with PDD-NOS (mean age 9.83; sd 2.17), and 13 children with SLI (mean age 9.17; sd 3.9) matched for age, sex and academic skills were explored for both receptive and expressive language skills. Prosody was also assessed with an intonation imitation task analyzed through automatic speech processing and compared to 70 typical developing controls matched for age and sex. A similar delay in phonology and vocabulary was observed in the three groups as were significant but variable differences between the groups in syntax, pragmatics and prosody. SLI showed correlations between chronological age and raw scores in all language tasks, while AD and PDD-NOS did not. Furthermore, SLI showed correlation within all raw scores in language tasks. Most of those correlations were also found in PDD-NOS but not in AD. In conclusion, these findings support the hypothesis that language skills in AD and SLI rely on different mechanisms, while PDD-NOS show an intermediate profile sharing some characteristics of both AD and SLI. They also suggest that expressive syntax, pragmatic skills and some intonation features could be considered as language differential markers of pathology, challenging the DSM-V proposal of broad criteria.

Research highlights
► We document language profiles in AD, PDD-NOS and SLI, including prosody.
► SLI showed a developmental profile.
► AD showed a pervasive profile.
► PDD-NOS showed an intermediate profile.
► Language skills in ASD challenge the DSM-V proposal of broad criteria.