Visual-spatial processing in children and adolescents with Down's syndrome: a computerized assessment of memory skills.

BACKGROUND: Several studies have identified better visual-spatial than verbal memory skills in children with Down's syndrome (DS); however, research in both typical development and DS points to a relative dissociation between visual and spatial memory processing, questioning the notion of a unitary visual-spatial memory construct. The insufficient and often contradictory results regarding the visual-spatial memory domain probably reflect the heterogeneity of memory tests employed by these studies and the different memory systems that they evaluate.
METHOD: We administered five visual-spatial memory tasks from the Cambridge Neuropsychological Test Automated Battery (CANTAB) to 25 children with DS and to 25 controls matched for mental age (MA) and basic psychomotor speed and accuracy. The memory tasks measure spatial span, visual and spatial recognition, paired associates learning and self-ordered search abilities.
RESULTS: The results confirm the relative sparing of the spatial short-term memory (STM) capacity in children with DS; however, as memory load increases, in recognition tasks, or when visual and spatial demands are combined, their performance is impaired compared with MA controls. The same impairment is generated by additional executive demands in the self-ordered search task, although search strategy is similar to the one presented by MA controls.
CONCLUSIONS: We did not find support for a visual vs. spatial dissociation in recognition memory. Performance impairment in the visual-spatial domain parallels the increase in working memory (WM) load or in the executive demands of the task. Possible neurobiological implications of the observed performance on the CANTAB tasks are also considered.