Multi-factorial deficits in developmental dyslexia

We investigated the role of some specific neuropsychological functions in the aetiology of developmental dyslexia. Sixty dyslexics and sixty-five age-matched controls were compared on their performance in dorsal - visual processing, visuo-spatial attention, implicit learning, frontal processing, and phonological short-term memory. Dorsal - visual processing was measured by means of a random-dot motion task; visuo-spatial attention was evaluated by a serial visual search task; as implicit learning measure, a serial reaction time task was used; frontal processing was analysed by means of the Wisconsin Cart Sort task; to evaluate the phonological short-term memory, a non-word repetition task was used. Results showed that the dyslexics had lower performances in comparison to the controls in dorsal - visual processing, visuo-spatial attention, and phonological short-term memory, and that these functions were significantly correlated with each other. These findings are in accordance with the hypothesis that developmental dyslexia is a multi-factorial deficit involving specifically dorsal - visual functions, spatial attention, and phonological processing.