Behavioral Phenotype Associations With Resting State <scp>EEG</scp> Signal Complexity and Power Spectral Density in Fragile X Syndrome

Fragile X Syndrome (FXS), an X-linked genetic condition, is associated with a wide range of phenotypic manifestations, namely intellectual disability (ID), autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), and atypical behaviors. Individuals with FXS present robust electrophysiological (EEG) alterations, notably on signal complexity and power spectral density (PSD) resting state measures. To which extent they are associated to specific behavioral phenotypes in the FXS population remains to be comprehensively addressed. This study aimed to investigate the relations between resting state EEG markers and the most frequently observed symptoms in FXS. EEG and behavioral data from 41 individuals with FXS aged between 7 and 34 years old were collected, and correlational approaches were used to analyze the associations between EEG markers and symptomatology. We observed positive associations between complexity in higher scales and non-verbal intelligence quotient (NVIQ). Reduced alpha power, a robust biomarker in FXS, was associated with more social avoidance, a hallmark in FXS. Decreased high gamma power was linked to hyperactive symptoms. Our results suggest powerful relations between known biomarkers and core symptoms in FXS, highlighting that EEG biomarkers correspond to symptom severity which further supports their potential as objective, translational treatment outcome measures.