Topography of syllable change-detection electrophysiological indices in children and adults with reading disabilities.

INTRODUCTION

Developmental dyslexia (DD) is a frequent language-based learning disorder. The predominant etiological view postulates that reading problems originate from a phonological impairment.

METHOD: We studied mismatch negativity (MMN) and Late Discriminative Negativity (LDN) to syllables change in both children (n=12; 8-12 years) and young adults (n=15; 14-23 years) with DD compared with controls.

RESULTS/DISCUSSION: The present study confirmed abnormal automatic discrimination of syllable changes in both children and adults with developmental dyslexia. MMN topographic, amplitude and latency group differences were evidenced, suggesting different brain mechanisms involved in elementary auditory stimulus change-detection in DD, especially in the left hemisphere. The LDN results demonstrated that the auditory disorder of temporal processing in DD children becomes more serious at late stages of information processing and that the apparent cerebral hypo reactivity to speech changes in DD actually may correspond to additional processes. The age-related differences observed in both MMN and LDN topographies, amplitudes and latency between subjects with DD and controls could indicate different developmental courses in the neural representation of basic speech sounds in good and poor readers, with a tendency to normalization with increasing age.

CONCLUSION

Our results showing atypical electrophysiological concomitants of speech auditory perception in DD strongly support the hypothesis of deviant cortical organization in DD.