The language phenotype of a small geographically isolated Russian-speaking population: Implications for genetic and clinical studies of developmental language disorder

Abstract

This article describes the results of an epidemiological study of developmental language disorder (DLD) in an isolated rural Russian population. We report an atypically high prevalence of DLD across all age groups when contrasted with a comparison population. The results are corroborated by a set of comparisons of school-aged children from the target population with their age peers and mean length of utterance matches from the comparison population. We also investigate the relationship between nonverbal cognition, verbal working memory, and expressive language performance in the population, and find statistically significant but small effect sizes. Finally, we describe the complex and heterogeneous structure of the phenotype in the population along with patterns of its vertical transmission on the basis of the exemplar pedigrees, and discuss the implications of our findings for genetic and clinical studies of DLD.

Language development in rural and urban Russian-speaking children with and without developmental language disorder

“…The majority of these children (n = 21) were additionally classified as TD using the Russian narrative task, a standardized elicited speech and language assessment protocol described in detail elsewhere (Rakhlin et al, 2013). Briefly, the protocol relies on the analysis of speech samples elicited using wordless storybooks according to a coding scheme that produces several expressive language measures (i.e., phonetic/prosodic development, wellformedness, number of complex structures, mean length of utterance, number of semantic/pragmatic errors, and lexical richness) in the domains of articulatory phonology, lexical, grammatical, and semantic/pragmatic language development.…”

“…Briefly, the protocol relies on the analysis of speech samples elicited using wordless storybooks according to a coding scheme that produces several expressive language measures (i.e., phonetic/prosodic development, wellformedness, number of complex structures, mean length of utterance, number of semantic/pragmatic errors, and lexical richness) in the domains of articulatory phonology, lexical, grammatical, and semantic/pragmatic language development. A child was considered TD if she demonstrated age- and narrative length-adjusted Z scores above −1 relative to the mean of the larger sample described elsewhere on all six measures (Rakhlin et al, 2013). …”

“…Children with DLD in the rural group were previously identified as DLD using the narrative task described above for the purpose of an epidemiological study of genetic bases of DLD (Rakhlin et al, 2013). They were classified as DLD if they showed low (i.e., a Z score of below −1) performance on at least two out of six expressive language measures.…”

“…First, given the dearth of research on child language development in Russian (both typical and atypical) and the current absence of published standardized instruments for the assessment of Russian language development (Lebedeva, 2014; Rakhlin et al, 2013) available to clinicians, educators, and researchers, we first aimed at using the sample data to obtain preliminary psychometric data on a new assessment of Russian language development (ORRIA). Correspondingly, we conducted a set of psychometric analyses aimed at 1) providing evidence for the reliability of the indicators of Russian language development obtained using the ORRIA assessment, and 2) evaluating ORRIA's items for the presence of content bias (also called differential item functioning or DIF),which could locally favor urban children and therefore distort the pattern of results of group comparisons.…”

Attentional But Not Pre-Attentive Neural Measures of Auditory Discrimination Are Atypical in Children With Developmental Language Disorder

“…The two experiments reported in the manuscript are part of a large epidemiological study of DLD in a Russian-speaking geographically isolated population. Importantly, since the population in question is environmentally and, presumably, genetically homogenous (Rakhlin et al, 2013c), it allowed us to overcome some of the methodological difficulties related to studying heterogeneous referred samples of children with DLD.…”