DEVELOPMENTAL TRAJECTORIES OF NEURAL OSCILLATORY ACTIVITY AND THEIR RELATIONSHIP TO LANGUAGE OUTCOMES IN YOUNG CHILDREN WITH FRAGILE X SYNDROME

Abstract

Fragile X Syndrome (FXS) is the most common inherited cause of intellectual disability, yet the developmental emergence of neural abnormalities observed in affected individuals remains poorly understood. This study characterized the developmental trajectory of neural oscillatory activity in young children with FXS (ages 3-9 years) using longitudinal EEG data from the FXLEARN clinical trial. The study used the FOOOF (Fitting Oscillations & One Over F) algorithm to separate periodic oscillatory components from aperiodic background activity, quantifying the theta-to- alpha frequency transition. Logistic regression estimated the age of this transition, and mixed effects models tested whether peak frequency and other FOOOF-derived features predicted language outcomes on the Weighted Communication Scale (WCS). The estimated transition occurred later than the benchmark reported for typical development, but a sensitivity analysis showed that the transition was unstable. Peak frequency did not significantly predict language outcomes beyond age, though its association with language was positive. These findings characterize early oscillatory development in FXS during a period when intervention may be most effective, while indicating that a single peak-frequency estimate has limited value as an individual- level marker.