This study study aimed to evaluate spatial function in subjects with Williams syndrome (WS) by using a large-scale task with multiple rewards and comparing the spatial abilities of WS subjects with those of mental age-matched control children. In the present spatial task, WS participants had to explore an open space to search nine rewards placed in buckets arranged according to three spatial configurations: a cross, a 3 x 3 matrix and a cluster composed by three groups of three buckets each. The findings demonstrate that WS individuals were impaired in efficiently exploring the environment and in building cognitive spatial maps. In exploring the three spatial configurations, they performed worse than control subjects on all parameters analyzed. In fact, WS individuals took more time to complete the task, made more errors, performed a reduced number of error-free trials, displayed lower search efficiency, exhibited shorter spatial spans, showed a higher number of no-visits and displayed marked tendencies to perseverate and to neglect some buckets. Furthermore, WS individuals showed disorganized explorative patterns in comparison to control children. WS influenced performances differentially as a specific effect of the susceptibility of the configurations to being explored in a principled way. In the cross configuration that had strong spatial constraints, both groups exhibited their worst performances. In the matrix configuration, the altered explorative strategies of the WS subjects primarily affected their central exploration. The performances in the cluster configuration indicated that chunking was a strategy of strength in both TD and WS groups. In conclusion, WS individuals' deficits exhibited in the present explorative test may be considered an index of their difficulties in spatial orientation and motion perception displayed in the real world. The marked impairment in spatial information processing is discussed in neuro-anatomical alterations reported in WS. (C) 2011 Elsevier Ltd. All rights reserved.
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