Plewko, J. 1, 2 , Chyl, K. 1 , Luniewska, M. 1, 2 , Banaszkiewicz, A. 1 , Debska, A. 1, 2 , Zelechowska, A. 1 , Marchewka, A. 3 & Jednorog, K. 1
1 Laboratory of Psychophysiology, Nencki Institute of Experimental Biology, PAS, Poland
2 Faculty of Psychology, University of Warsaw, Poland
3 Laboratory of Brain Imagining, Neurobiology Center, Nencki Institute of Experimental Biology, PAS, Poland
Learning letter-speech sound association is the first and critical step for reading development. Previous studies showed reduced responses to letters and speech sounds as well as no congruency effects in dyslexic subjects. Little is known however if such deficits are already present in children with familial risk for dyslexia (FHD+).
54 FHD+ and 39 FHD- children (mean age = 7 years) underwent fMRI scanning during which four experimental conditions were presented (letters, speech sounds, congruent and incongruent letter-speech sound associations).
FHD+ children showed weaker activity for processing speech sounds in the left superior and inferior temporal gyri and in the left fusiform gyrus, while they had higher activity than FHD- children in the right intraparietal lobe and interior frontal gyrus. FHD+ children had also reduced activity for letters in the anterior temporal lobes bilaterally.
Interestingly, in multisensory conditions, incongruent vs. congruent letter-speech sound association produced higher activation, observed for less transparent orthographies. In this condition FHD+ compared to FHD- children had significantly reduced activity mainly in the left tempo-parietal cortex.
Our results suggest that some brain activity differences observed in dyslexic children and adults are already visible in beginning readers at risk of dyslexia.