Neuropsychological correlates of word identification in Down syndrome.

In order to better understand the neuropsychological underpinnings of the relative strength in word identification in individuals with Down syndrome, the performance of children and adolescents with Down syndrome (N=29) was compared to the performance of a nonverbal-IQ matched group of children and adolescents with developmental disabilities of mixed etiologies (N=20) on measures letter/word identification and cognitive-linguistic functioning. Though no between-group differences were observed for letter/word identification or visual processing performance, individuals with Down syndrome showed significantly poorer verbal short-term memory and receptive vocabulary skills. In terms of neuropsychological correlates of letter/word identification, significant linear associations were observed between letter/word identification (K-ABC reading/decoding) and verbal short-term memory (K-ABC number recall), as well as receptive vocabulary (PPVT-III) and visual processing (MVPT-R) in both groups. However, when only children with word identification competence (as opposed to letter identification competence) were included in analyses, visual perception scores (total MVPT-R) were significantly associated with word identification in the Down syndrome group, but not in the mixed comparison group. Implications for etiology-specific instructional approaches are discussed.