Estudio de la negatividad de discrepancia auditiva en dos subtipos de niños con dislexia del desarrollo

Neuropsychological characterization of subtypes in developmental dyslexia contradicts the idea of the existence of a unique cognitive mechanism damaged in this entity. The linguistic components of evoked related potentials (ERP) provide a functional window to find the underlying dysfunction within a temporal sequence of processing stages related with reading. The aim of this study was to evaluate with the mismatch negativity (MMN) in two subtypes of developmental dyslexia. Fourteen dyslexic children and seven siblings were examined. Using a words and pseudowords reading task, the dyslexic group was divided into two subtypes, phonologic or surface dyslexics respectively. A mismatch negativity (MMN) was measured in all this subjects, using the classical paradigm of auditory discrimination of pure tones (1.000 and 1.200 Hz) presented sequentially with a relative probability of 0.15 y 0.85 and 600 ms of interstimulus interval. An MMN was obtained to both, control subjects and the surface deficit group. Dyslexics with phonological deficit haven't got this component. Differences in electrophysiological patterns of these two subtypes of developmental dyslexia, contradict the idea of a unique cognitive mechanism damaged in this impairment. The highest differences in the amplitude in MMN found in the phonologic dyslexics suggest a more generalized underlying difficulty in central auditory processing.