Astrid, D. V. 1, 2 , Sophie, V. 1, 2 , Vanderauwera, J. 1, 2 , Ghesquière, P. 2 & Wouters, J. 1
1 Research Group Experimental ORL, Dept. Neurosciences, KU Leuven, Belgium
2 Parenting and Special Education Research Unit, Faculty of Psychology and Educational Sciences, KU Leuven, Belgium
The present study aims to examine synchronization of neural oscillations in a broad frequency range including theta, alpha, beta and low-gamma rates. The main research question is whether neural synchronization to modulations relevant for speech perception in dyslexic readers differs from normal readers. Given the importance of low-rate modulations for speech intelligibility, differences in the cortical processing of slow temporal variations could relate to the core phonological processing problems found in children and adults with dyslexia.
Auditory steady-state responses (ASSRs) were recorded in normal-reading and dyslexic adolescents. Participants listened to amplitude modulated noise stimuli, modulated at 4 Hz (theta), 10 Hz (alpha), 20 Hz (beta) and 40 Hz (low-gamma). Stimuli were presented in three modalities: unilateral left, unilateral right and bilaterally.
Our results reveal atypical neural synchronization of alpha and beta range oscillations in dyslexic readers. These effects are present in both hemispheres and seems to be more pronounced for unilateral stimulation modalities. We found no group differences for theta and low-gamma range synchronization.
To our knowledge, this is the first EEG study to examine auditory synchronization of neural oscillations using such a broad range of speech envelope rates. In particular the inclusion of alpha rate modulations makes this study unique.