Nature of the working memory deficit in fragile-X syndrome.

Working memory performance in a group of young Fragile X males with FMR-1 full mutation was compared to a learning disabled comparison group comprising Down's syndrome males and two control groups of mainstream schoolchildren. Performance was assessed on a battery of tasks tapping the three components of working memory-phonological loop, visual-spatial sketch pad, and the central executive. The results indicated that the Fragile X group displayed a general impairment on working memory tasks that cannot be attributed to a single working memory component per se. Instead, the results suggest that Fragile X males have a working memory deficit that may be attributed to how much attentional resource a specific task requires and their overall available executive capacity, irrespective of the working memory subsystem.