Verbal short-term memory deficits in Down syndrome: phonological, semantic, or both?

Nancy Raitano Lee,Bruce F Pennington,Janice M Keenan

doi:10.1007/s11689-009-9029-4

Abstract

The current study examined the phonological and semantic contributions to the verbal short-term memory (VSTM) deficit in Down syndrome (DS) by experimentally manipulating the phonological and semantic demands of VSTM tasks. The performance of 18 individuals with DS (ages 11–25) and 18 typically developing children (ages 3–10) matched pairwise on receptive vocabulary and gender was compared on four VSTM tasks, two tapping phonological VSTM (phonological similarity, nonword discrimination) and two tapping semantic VSTM (semantic category, semantic proactive interference). Group by condition interactions were found on the two phonological VSTM tasks (suggesting less sensitivity to the phonological qualities of words in DS), but not on the two semantic VSTM tasks. These findings suggest that a phonological weakness contributes to the VSTM deficit in DS. These results are discussed in relation to the DS neuropsychological and neuroanatomical phenotype.

Highlights

The current study examined the phonological and semantic contributions to the verbal short-term memory (VSTM) deficit in Down syndrome (DS) by experimentally manipulating the phonological and semantic demands of VSTM tasks
Both hypotheses could be supported by our results, because it is possible that deficits in both phonology and semantics may be contributing to the VSTM deficit in DS
If the phonological hypothesis is supported, a group by condition interaction is anticipated on the phonological similarity task, such that the DS group is less affected by the phonologically similar or confusable words than controls

Summary

Phonological hypothesis

If a phonological deficit underlies weak VSTM skills in DS, performance on tasks tapping the phonological qualities of words will differ from MA matched controls and reflect a less mature pattern of performance, including reduced sensitivity to the phonological qualities of words and greater impairments on tasks that are phonologically demanding, such as nonword tasks

Semantic hypothesis

Participants

Results

Discussion