A specific deficit in visuospatial simultaneous working memory in Down syndrome

Recent studies have demonstrated that individuals with Down syndrome (DS) present both central and verbal working memory deficits compared with controls matched for mental age, whereas evidence on visuospatial working memory (VSWM) has remained ambiguous. The present paper uses a battery of VSWM tasks to test the hypothesis that individuals with DS can also encounter specific difficulties in VSWM. Four tasks were administered to 34 children and adolescents with DS and 34 controls matched for verbal mental age. In two of these tasks, participants had to remember a series of locations sequentially presented on a matrix (spatial-sequential WM); in another two, they had to remember locations simultaneously presented (spatial-simultaneous WM). Results showed that individuals with DS are poorer than controls in the spatial-simultaneous tasks, but not in the spatial-sequential tasks. These findings were not due to a difference in speed of visuospatial processing. In fact, when performances of the two groups in VSWM were compared using speed measures as covariates, differences between groups remained. It is suggested that the simultaneous VSWM deficit of individuals with DS could be due to the request for processing more than one item at a time.