ABSTRACT
Although reduced verbal span is well documented in individuals with developmental dyslexia, the existing data on visual-spatial span are inconclusive. The aim of the present study was to ascertain whether the working memory deficit in developmental dyslexia is confined to verbal material or whether it also involves visual-object and visual-spatial information. Results document deficits on span tasks tapping verbal, visual-spatial, and visual-object working memory in dyslexic children and indicate that the working memory deficit in developmental dyslexia is not limited to dysfunction of phonological components but also involves visual-object and visual-spatial information.
Subject(s)
Articulation Disorders/etiology , Dyslexia/complications , Memory Disorders/etiology , Memory, Short-Term/physiology , Adolescent , Age Factors , Attention/physiology , Child , Female , Humans , Male , Neuropsychological Tests , Photic Stimulation , Visual Perception/physiologyABSTRACT
Reading acquisition requires, in addition to appropriate phonological abilities, accurate and rapid selection of sublexical orthographic units by attentional letter string parsing. Spatio-temporal distribution of attentional engagement onto 3-pseudoletter strings was studied in 28 dyslexic and 55 normally reading children by measuring attentional masking (AM). AM refers to an impaired identification of the first of two sequentially presented masked objects (O1 and O2). In the present study, O1 was always centrally displayed, whereas the location of O2 (central or lateral) and the O1-O2 interval were manipulated. Dyslexic children showed a larger AM at the shortest O1-O2 interval and a sluggish AM recovery at the longest O1-O2 interval, as well as an abnormal lateral AM. More importantly, these spatio-temporal deficits of attentional engagement were selectively present in dyslexics with poor phonological decoding skills. Our results suggest that an inefficient spatio-temporal distribution of attentional engagement - probably linked to a parietal lobule dysfunction - might selectively impair the letter string parsing mechanism during phonological decoding.
Subject(s)
Attention/physiology , Dyslexia/physiopathology , Reading , Adolescent , Analysis of Variance , Child , Eye Movements/physiology , Female , Humans , MaleABSTRACT
The reduced verbal long-term memory capacities often reported in dyslexics are generally interpreted as a consequence of their deficit in phonological coding.The present study was aimed at evaluating whether the learning deficit exhibited by dyslexics was restricted only to the verbal component of the long-term memory abilities or also involved visual-object and visual-spatial domain. A further goal of the present study was to investigate the predictive value of non-verbal long-term memory abilities with respect to word and non-word reading in dyslexic children.In accordance with these aims, performances of 60 dyslexic children were compared with that of 65 age-matched normal readers on verbal, visual-spatial and visual-object task.Results documented a generalized impairment of episodic long-term memory capacities in dyslexic children and the results did not vary as a function of children's age.Furthermore, in addition to verbal measures, also individual differences in non-verbal long-term memory tasks turn out to be good predictors of reading difficulties in dyslexics.Our findings indicate that the long-term memory deficit in dyslexia is not limited to the dysfunction of phonological components but also involves visual-object and visual-spatial aspect, thus suggesting that dyslexia is associated to multiple cognitive deficits.
