Lizarazu, M. 1 , Lallier, M. 1 , Bourguignon, M. 2 , Carreiras, M. . 1, 3 & Molinaro, N. . 1, 3
1 BCBL, Basque centre on Cognition, Brain and Language, San Sebastian/Donostia, Spain
2 Aalto University School of Science, Aalto, Finland
3 Ikerbasque, Basque Foundation for Science, Bilbao, Spain
According to the Asymmetric Sampling in Time theory, hemispherical asymmetries in the neural structure of the auditory cortex make the left hemisphere more sensitive to short timescales (25-50 ms: ~40 Hz) and the right to longer timescales (250 ms: ~4 Hz). Inappropriate sampling of the auditory signals could be responsible for the phonological difficulties of dyslexia. Previous studies reported both weak left hemisphere synchronization for fast oscillatory components of speech and weak right hemisphere synchronization for slow oscillations. No study evaluated both low and high frequency synchronization in the same population.
We focused on a different linguistic population (Spanish monolinguals with and without dyslexia) and evaluated how these effects change with age (studying both adults and children). Magnetoencephalographic activity was recorded whilst participant watched a silent movie and hear stimuli presenting amplitude modulated noise at low (2, 4, 7 Hz) and high frequencies (30, 60 Hz).
Our results indicate that both children and adult dyslexic´s present differences at high frequencies compare to their corresponding matched groups, suggesting that synchronization effects are a consequence of how language impacts on dyslexia. Furthermore, in dyslexic children low frequency differences seem to play an important role too, indicating that the auditory synchronization phenomenon changes with age.