Investigating the Central Executive in Adult Dyslexics :

There is long-standing evidence for verbal working memory impairments in both children and adults with dyslexia. By contrast, spatial memory appears largely to be unimpaired. In an attempt to distinguish between phonological and central executive accounts of the impairments in working memory, a set of phonological and spatial working memory tasks was designed to investigate the key issues in working memory, task type, task demands (static, dynamic, and updating), and task complexity. Significant differences emerged between the dyslexic and non-dyslexic participants on the verbal working memory tasks employed in Experiment 1, thereby providing further evidence for continuing dyslexic impairments of working memory into adulthood. The nature of the deficits suggested a problem with the phonological loop, with there being little evidence to implicate an impairment of the central executive. Due to the difficulties associated with separating verbal working memory and phonological processing, however, performance was investigated in Experiment 2 using visuo-spatial measures of working memory. The results of the visuo-spatial tasks indicated no between-group differences in static spatial memory, requiring the short-term storage of simultaneously presented information. In almost all conditions there were no betweengroup differences in dynamic spatial memory that demands the recall of both location and order of stimuli presented sequentially. However, a significant impairment occurred on the dynamic task under high memory updating load, on which dyslexic adults showed non-phonological working memory deficits. In the absence of an explanation in terms of verbal recoding, this finding is interpreted in terms of a central executive or automaticity impairment in dyslexia.