The nature of the spatial deficit in young females with Fragile-X syndrome: a neuropsychological and molecular perspective.

Spatial performance in a group of young Fragile-X syndrome females with FMR-1 full mutation was compared to two control groups of mainstream schoolchildren. Performance was assessed across a wide range of spatial tasks including visuo-spatial, visuo-construction, visuo-motor, visuo-perception and spatial-memory. A spatial deficit emerged only on those tasks which comprised a visuo-constructive component, with the Fragile-X group performing worse overall. All other tasks were performed at a comparable level across the three groups. Molecular analysis of the lymphocyte DNA found minimal evidence for a correlation between expansion size and spatial performance. In addition, there was no evidence for a correlation between the proportion of active to inactive unmethylated FMR-1 genes (activation ratio) and spatial performance. These results conflict with recent reports of a correlation between activation ratio and intellectual functioning.