Sex chromosome trisomies are not associated with atypical lateralization for language

Abstract

Aim: To test the hypothesis that sex chromosome trisomies (SCTs) are associated with reduced left lateralization for language. Method: Using a cross-sectional design, language laterality was measured during an animation description task using functional transcranial Doppler ultrasonography. Data were available for 75 children with an SCT (47,XXX females [n=26], 47,XXY males [n=25], 47,XYY males [n=24]; mean age 11y 4mo [SD 3y 10mo]) and 132 comparison children with typical karyotypes (69 males, 63 females; mean age 9y 1mo [SD 1y 7mo]). Results: Lateralization for language did not differ between the SCT and comparison groups, either in mean laterality index or relative frequency of each laterality category. There were no differences when splitting the group with an SCT by trisomy. Handedness showed no group effects. Interpretation: Our data provide no evidence for disrupted lateralization for language in SCTs. The brain basis of the cognitive phenotype in SCTs is unlikely to be a failure of the left hemisphere to specialize for language, as previously suggested. What this paper adds: Children with a sex chromosome trisomy (SCT) have typically lateralized language. This disproves theories linking language problems to hemispheric specialization in SCTs.