Visual and spatial working memory dissociation: evidence from Williams syndrome.

This study aimed at investigating the possible dissociation between visual and spatial working memory (WM) by means of two different experiments. In the first experiment, a WM test for visual material and for spatial information was given to a group of 202 normally developing children (chronological age 7 years 5 months, SD 1.6 years; 109 males, 93 females). Results document a different developmental trend in the two span tests. In the second experiment, we presented the same visual and spatial WM tests to a group of 13 individuals with Williams syndrome (WS), seven males and six females (chronological age mean 18 years 3 months, SD 5.1; mental age mean 7 years 2 months, SD 1.5 years), and to a control group of 26 typically developing children 14 males and 12 females matched for mental age (mean 7 years 2 months, SD 1.4). The results of this second experiment show that, on average, the spatial span obtained by individuals with WS was significantly lower than control participants, but visual span was comparable in the two groups. Our data support the hypothesis of a dissociation within the visuo-spatial sketch pad slave system in the WM model.