Molinaro, N. 1, 2 , Lizarazu, M. 1 , Lallier, M. 1 , Bourguignon, M. 1 & Carreiras, M. 1, 2
1 BCBL, Basque center on Cognition, Brain and Language
2 Ikerbasque, Basque Foundation for Science
It has been recently suggested that the phonological disorder in dyslexia is the result of the malfunctioning of the primary auditory regions. Taking advantage of the excellent temporal resolution of magnetoencephalography (MEG) we analyzed in two studies the functionality of the auditory system in developmental dyslexia. We studied the neural entrainment (i.e., the reactivity of a neural network to synchronize with the rhythmic properties of an external stimulus) to the multiple frequencies of both the speech and non-speech signals, i.e., delta (~1Hz), theta (~4-7 Hz) and gamma (> 30 Hz) bands oscillatory stimulation. The results highlighted that: (i) dyslexic readers show an atypical specialization of the auditory cortex to both low and high frequency amplitude modulations; (ii) such specialization is related to the anatomical properties of the auditory brain regions; (iii) neural synchrony to low-frequency speech oscillations in primary auditory regions hinders higher-order speech processing steps and the sampling of high frequency speech components. Such atypical auditory entrainment has the strong potential to cause severe consequences for both phonological and reading skills. Our findings, thus, strengthen proposals assuming that low-frequency acoustic entrainment hierarchically drives processing of higher speech frequencies and its impairment contributes to the phonological disorders in developmental dyslexia.