The Children's Nonword Repetition Test (CNRep) was given 39 children with persistent language impairment (LI), 13 with a history of having received speech-language therapy (resolved LI), and 79 controls, all aged from 7 to 9 years. The children with LI were twins who had participated in a previous genetic study. Children with resolved LI, as well as those with persistent LI, were significantly impaired on the CNRep. Comparisons of MZ and DZ twins indicated significant heritability of a CNRep deficit. It is concluded that CNRep provides a marker of the phenotype of heritable forms of developmental language impairment.
SUMMARY
Concordance rates were compared for 63 monozygotic (MZ) and 27 dizygotic (DZ) same‐sex twin pairs, aged seven years and over, selected because at least one twin met diagnostic criteria for specific speech or language impairment. There was significant heritability for developmental speech and language disorder, defined according to DSM‐III‐R criteria. When the definition of the phenotype was broadened to include those with a past history of disorder and those with a less pronounced discrepancy between verbal and non‐verbal ability, concordance for MZ twins was close to 100 per cent, and that for DZ twins approximately 50 per cent. There was also close similarity between concordant twins for type of disorder. There is good evidence that genetic factors play a role in the aetiology of speech and language impairment; twin data may help us arrive at a clearer conception of the phenotype as well as quantifying the extent of the genetic contribution.
RÉSUMÉ
Bases génétiques des troubles spécifiques de langage: évidence à partir d'une étude de jumeaux
Les taux de concordance ont été compareés entre 63 paires de jumeaux monozygotes et 27 paires dizygotes de même sexe, âgés de sept ans ou plus et sélectionnés du fait que l'un des jumeaux au moins remplissait les critères diagnostiques pour un trouble spécifique de parole ou de langage. II y avail une héritabilité significative pour les troubles développementaux de parole et de langage, scion les critéres du DSM‐III‐R. Quand la définition du phénotype était étendue au cas de troubles passés et à un écart moins prononcé entre capacityés verbales et non verbalcs, la concordance pour les jumeaux monozygotes était proche de 100 pour cent et elle était d'environ 50 pour cent pour les jumeaux dizygotes. 11 y avait également une correspondance étroite entre jumeaux pour le type de troubles. 11 y a done de bonnes raisons pour penser que les facteurs génétiques jouent un rôle dans l'étiologie des troubles de parole et de langage; ces données de jumeaux peuvent nous aider à avoir une conception plus claire du phénotype, aussi bien que des aspects quantifyés de la contribution génétique.
ZUSAMMENFASSUNG
Genetische Grundlage der spezifischen Sprachstörung: Befunde aus einer Zwillingsstudie
Es wurden die Konkordanzraten von 63 monozygoten (MZ) und 27 dizygoten, gleichgeschlechtlichen (DZ) Zwillingspaarcn im Alter von sieben Jahren oder darüber verglichen, die ausgewählt worden waren, weil mindestens ein Zwillingskind die diagnostischen Kriterien für eine spezifische Sprach‐oder Sprachverständnisstörung erfüllte. Es bestand eine signifikante Erblichkeit für die Entwicklung von Sprach‐und Sprachverständnisstörungen, definiert nach den DSM‐III‐R Kriterien. Erweiterte man die Definition des Phänotyps und nahm die mit einer früheren Störung in der Anamnese und die mit einer weniger ausgeprägten Diskrepanz zwischen verbalen und non‐verbalen Fähigkeiten hinzu, war die Konkordanz für MZ Zwillinge nahezu 100 Prozent und die für DZ Zwillinge ungefähr 50 Prozent. Es besteht auch eine weitg...
A sample (n=48) of eight-year-olds with specific language impairments is compared with age-matched (n=55) and language matched controls (n=55) on a range of tasks designed to test the interdependence of language and mathematical development. Performance across tasks varies substantially in the SLI group, showing profound deficits in production of the count word sequence and basic calculation and significant deficits in understanding of the place-value principle in Hindu-Arabic notation. Only in understanding of arithmetic principles does SLI performance approximate that of age-matched-controls, indicating that principled understanding can develop even where number sequence production and other aspects of number processing are severely compromised.
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