[PS-1.23] Evidence in favor of the sluggish attentional shifting hypothesis of dyslexia: A magnetoencephalography study in dyslexic children

Molinaro, N. 1 , Lallier, M. 1 , Lizarazu, M. 1 , Bourguignon, M. 2 & Carreiras, M. 1, 3

1 BCBL, Basque center on Cognition, Brain and Language, Donostia/San Sebastian, Spain
2 Université Libre de Bruxelles, Bruxelles, Belgium
3 Ikerbasque, Basque foundation for Science, Bilbao, Spain

Phonological difficulties in developmental dyslexia are believed to arise from a more general auditory processing deficit, hindering phonological analysis of speech. A magnetoencephalography (MEG) study shows atypical neural oscillations in dyslexic participants to slow auditory stimulus modulations (~2 Hz), thought to contribute to impaired amplitude rise time analysis in speech (Hämäläinen et al., 2012). Another reports abnormal neural oscillatory activity restricted to high frequency oscillatory response (~30 Hz), interpreted as a ?phonemic oversampling? in dyslexic participants (Lehongre et al., 2011). In the present MEG study, we compared phase locking responses to amplitude modulated white noise at different modulation rates in children with (n = 8; 12.4 y.o ± 3) and without (n = 7; 12.8 y.o ± 2.5) dyslexia. Each frequency rate (2, 4, 7, 10, 15, 30, 60 Hz) was randomly presented in 10s-blocks 25 times. Participants were watching a silent movie whilst listening to the modulated noise. For each rate, segments including 2 oscillatory cycles were analysed. Inter-trial phase locking between segments was estimated using gradiometer data for each participant. Results showed significant effects in the right hemisphere at 4 Hz [p<0.05, Figure 1, right panel] and in the left hemisphere at 15 Hz [p<0.05, Figure 1, left panel]. These results show abnormal neural synchronisation i) in slow auditory frequency ranges (i.e., 4 Hz), more prominent in the auditory cortex of the right hemisphere in accordance with the ?temporal sampling? hypothesis of Goswami (2011) and ii) at 15Hz in the left hemisphere. This last result is discussed in light of the sluggish attentional shifting theory of dyslexia (Hari and Renvall, 2001).