EEG Signal Complexity Is Reduced During Resting-State in Fragile X Syndrome.

Mélodie Proteau-Lemieux,Valérie Côté,Hazel Maridith Barlahan Biag,Sarah Lippé,Charles-Olivier Martin,Kristian Agbogba,Anne-Marie Bélanger,François Bolduc,Inga Sophia Knoth,Andrea Schneider,Randi Hagerman,Cory Rosenfelt,Flora Tassone,Angela John Thurman,Sébastien Jacquemont,David Hessl,Leonard J Abbeduto

doi:10.3389/fpsyt.2021.716707

Abstract

Introduction: Fragile X syndrome (FXS) is a genetic disorder caused by a mutation of the fragile X mental retardation 1 gene (FMR1). FXS is associated with neurophysiological abnormalities, including cortical hyperexcitability. Alterations in electroencephalogram (EEG) resting-state power spectral density (PSD) are well-defined in FXS and were found to be linked to neurodevelopmental delays. Whether non-linear dynamics of the brain signal are also altered remains to be studied.Methods: In this study, resting-state EEG power, including alpha peak frequency (APF) and theta/beta ratio (TBR), as well as signal complexity using multi-scale entropy (MSE) were compared between 26 FXS participants (ages 5–28 years), and 77 neurotypical (NT) controls with a similar age distribution. Subsequently a replication study was carried out, comparing our cohort to 19 FXS participants independently recorded at a different site.Results: PSD results confirmed the increased gamma, decreased alpha power and APF in FXS participants compared to NT controls. No alterations in TBR were found. Importantly, results revealed reduced signal complexity in FXS participants, specifically in higher scales, suggesting that altered signal complexity is sensitive to brain alterations in this population. The replication study mostly confirmed these results and suggested critical points of stagnation in the neurodevelopmental curve of FXS.Conclusion: Signal complexity is a powerful feature that can be added to the electrophysiological biomarkers of brain maturation in FXS.

Highlights

Fragile X syndrome (FXS) is a genetic disorder caused by a mutation of the fragile X mental retardation 1 gene (FMR1)
Signal complexity is a powerful feature that can be added to the electrophysiological biomarkers of brain maturation in FXS
We first analysed power spectral density (PSD) in order to verify if we can replicate the results previously reported in the literature

Summary

Introduction

Fragile X syndrome (FXS) is a genetic disorder caused by a mutation of the fragile X mental retardation 1 gene (FMR1). Fragile X syndrome (FXS) is an X-linked genetic disorder caused by dynamic mutations of the fragile X mental retardation 1 gene (FMR1), leading to alterations, or to complete absence of the fragile X mental retardation protein (FMRP), its encoded protein. Its absence leads to excessive protein synthesis [2], which is associated with impaired synaptic plasticity [3]. FXS is the most common monogenetic cause of inherited intellectual disability (ID) and single gene cause of autism spectrum disorder (ASD). It is associated with physical, behavioral, cognitive and emotional impairments. The clinical features of patients with FXS vary significantly from one individual to another, especially between men and women, due to the unaffected second X chromosome present in women

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