Early neonatal EEG markers for dyslexia risk: a pilot study.

INTRODUCTION Dyslexia is a neurodevelopmental disability in learning to read that has a strong heritable component, affecting up to 10% of the population. Early identification of high-risk individuals could facilitate earlier diagnosis and provision of intervention support for affected children. Although the neurobiological mechanisms underlying dyslexia are still unclear, one hypothesis suggests an impairment of neural mechanisms for phonological (speech sound) processing, arising from inaccurate neuronal oscillatory phase-locking to the temporal structure of speech (e.g. syllables and stress patterns). This pilot study aimed to compare phase-locking acuity to rhythmic speech in newborns with familial risk of dyslexia compared to controls, in order to identify possible early markers for dyslexia risk. METHODS Thirty-two healthy term newborns, of which 12 had a familial risk of dyslexia (defined as the presence of ≥ 1 parent and/or sibling with dyslexia) and 20 controls (no familial history of dyslexia) were included in the study. At ≤ 7 days of life (median 3 days, interquartile range 1-5), the infants underwent an EEG recording including 20 minutes of resting state and 20 minutes of passive listening to spoken nursery rhymes. EEG was acquired using BrainVision software, and analysed in Matlab. To assess acuity of speech processing, the Phase-Locking Value (PLV) was computed between infants’ oscillatory response and the speech amplitude envelope. RESULTS Preliminary findings indicate a group difference between high-risk and control infants’ oscillatory phase-locking acuity. This difference was most pronounced over the right temporal cortex. Our neural results indicated that, over right temporal cortical regions (electrodes T4 + F8), high-risk neonates showed significantly poorer neural oscillatory processing of low-frequency (1-3 Hz) speech sounds than low-risk neonates (F[1,27] = 5.3, p < 0.05). Fig. 1 shows phase-locking accuracy over right temporal cortex (T4 electrode) for different speech frequencies for low-risk (blue) and high-risk infants (red). CONCLUSIONS Our preliminary results suggest that the evaluation of neuronal oscillatory phase-locking acuity in neonates within the first week of life might represent a potential neonatal biomarker for dyslexia risk. However, larger longitudinal studies are needed to assess the long-term predictive value of early phase-locking indices on children’s language and reading development.