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Deficits in neural activation during silent single-word reading in developmental dyslexia: An MEG study.
Poster Session B, Wednesday, September 30, 4:30 - 6:30 pm, Wangari Maathai
Tatiana Bolgina1, Ilya Samoylov1, Georgii Lonshakov1, Ekaterina Shcheglova1, Militina Gomozova1, Tatyana Yashina2, Vardan Arutiunian3, Olga Dragoy1; 1Center for Language and Brain, HSE, Moscow, Russia, 2Center for Speech Pathology and Neurorehabilitation, Moscow, Russia, 3Azrieli Research Center of CHU Sainte-Justine, Montreal, Quebec, Canada
Despite normal schooling and print exposure, children with developmental dyslexia (DD) fail to acquire adequate reading skills, yet the neural mechanisms underlying this disorder remain poorly understood, limiting early identification and intervention (Noordenbos et al., 2013; Shaywitz et al., 2006). While behavioral measures only capture reading outcomes, neurophysiological methods such as Magnetoencephalography (MEG) can track the spatiotemporal dynamics of reading, which unfold across three successive components (visual feature analysis, letter-string analysis, and lexical-semantic analysis) (Salmelin, 2007). Existing developmental studies have yielded inconsistent findings regarding group differences between typically developing (TD) children and those with DD, particularly at the letter-string and lexical-semantic stages (Araújo et al., 2012; Bakos et al., 2018; Hasko et al., 2013; Kemény et al., 2018; Sun et al., 2023), and no study to date has systematically examined word frequency modulation in these components in both TD and DD children. The present study therefore aims to use MEG to investigate the effects of word frequency and lexicality on neural dynamics during silent word reading in school-aged TD and DD native Russian-speaking children, in order to identify precisely when and where processing disruptions emerge in dyslexia. MEG was recorded from 30 TD children (12 female; mean age = 9.7 years, SD = 1.3, range = 7.2-12) and 27 children with DD (10 female; mean age = 9.9 years, SD = 1.17, range = 7.2-12) during a single word reading task involving high-frequency words, low-frequency words, and pseudowords. Contrary to prior evidence emphasizing early lexical differentiation, neither group showed significant sensitivity to word frequency or lexicality, suggesting a uniform decoding strategy during silent reading in both TD and DD children. However, direct group comparisons revealed profound differences in activation strength: the DD group exhibited significant bilateral reduction of activation in the occipito-temporal cortex and lower activation in the left superior temporal cortex, despite similar inter-hemispheric temporal dynamics between groups. Crucially, older TD children showed increased neural activation of the left temporal cortex, indicating ongoing specialization of the reading network, whereas this age-related increase was absent in the DD group, suggesting a stagnation in the development of reading-related neural circuits. These findings indicate that the neural deficit in dyslexia is characterized by a fundamental failure to activate neural resources to a sufficient amplitude, rather than an inability to differentiate lexical properties.
Topic Areas: Disorders: Developmental, Reading