Fragile X Syndrome (FXS) is a complex neurodevelopmental disorder caused by a mutation on the X chromosome. Scientists have investigated FXS extensively in both humans and animals. Thus far, phenotypic rescue in animal models has not resulted in treatment breakthroughs in humans, though some important discoveries have been made. Research has shown that individuals with FXS process sounds differently than those in the typical population, and they also show baseline differences in brain activity, including high gamma activity, increased theta activity, and decreased alpha activity. The investigators' central hypothesis is that these alterations in brain activity (specifically alpha and gamma activity) impair the brain's ability to process new information, thereby impeding cognitive functioning and increasing sensory sensitivity. The investigators propose that auditory entrainment, a technique that involves playing special sounds through headphones, will normalize brain activity in individuals with FXS and lead to increased cognitive function and decreased sensory hypersensitivity.

Fragile X Syndrome (FXS) is an exemplar monogenetic neurodevelopmental disorder (NDD) where a tremendous body of multi-species translational research has elucidated the underlying molecular pathophysiology, and more recently, in-depth electrophysiology of cortical function. Thus far, phenotypic rescue in animal models has not resulted in treatment breakthroughs in humans. Central to this discrepancy is a poor understanding of the constituent neurodynamics of averaged group effects and individual variability in human brain activity as related to higher-level cognitive symptomatology and clinical phenotype. The investigators' large collection of preliminary data demonstrates that individuals with FXS do not mount precise neural responses to the sensory auditory chirp and, instead, have "noisy" asynchronous gamma activity. Furthermore, a marked reduction in alpha power suggests altered thalamocortical function, reducing the ability to detect signal from noise and representing potential tractable targets for "bottom-up" entrainment. This approach involves three scientific aims, which, if addressed, would ascertain underlying mechanisms that may alleviate sensory and cognitive impairments. First, the investigators will study transient, non-continuous features (neurodynamics) of alpha and gamma oscillations in resting-state EEG and sensory auditory chirp that model patient-level heterogeneity and constitute group effects (Aim 1A), and will also identify what, if any, of these novel features are conserved in the Fmr1-/-KO using preexisting murine EEG data and represent patient subgroups (Aim 1B). Second, the research team will extend into cognition by studying neurodynamics and circuit modeling associated with statistical learning (SL), which shares similar neural mechanisms to the sensory auditory chirp (Aim 2). Third, the investigators will use individualized closed-loop alpha auditory entrainment (AAE) to attempt the normalization of neural signatures of the sensory auditory chirp and SL tasks (Aim 3). Aim 1 and 2 findings will provide critical data to optimize closed-loop parameters of AAE to serve as a "bottom- up" neural probe to understand the mechanics of disorder-relevant circuit activity through perturbation of thalamocortical drive. Ascertaining the mechanisms underlying these alterations would have a high clinical impact, especially to enhance early intervention to alter the trajectory of intellectual development in which no definitive treatments are available.

Inclusion Criteria:

• FXS Cohort: 1) Aged 5-10 years, inclusive; 2) Patient has full FMR1 mutation confirmed by genetic testing.
• ASD Cohort: 1) Aged 5-10 years, inclusive; 2) Have no known genetic mutation; 3) Have documentation of ASD diagnosis; 4) Score ≤ 15 on SCQ screen; 5) Be in good health per investigator.
• TDC Cohort: 1) Aged 5-10 years, inclusive; 2) Have no known genetic mutation; 3) Have documentation of ASD diagnosis; 4) Score ≤ 15 on SCQ screen; 5) Be in good health per investigator; 6) Patient has met normal developmental milestones; Patient has no family history of heritable neuropsychiatric disorders; 7) Patient has an IQ greater than 85 on the Stanford-Binet; 8) Score ≤8 on an SCQ screen.

Exclusion Criteria:

• All subjects: 1) Patient has auditory or visual impairments that cannot be corrected; 2) History of substance abuse or dependence within the past 6 months

all collected, deidentified IPD

upon publication of results

Research data gathered as part of this study may be shared and provided to other investigators affiliated with the Neurobehavioral and Neurology Research Teams at CCHMC for the purpose of data sharing. If participants are enrolled in multiple studies, their research data will be shared across studies to reduce participant burden and avoid duplication of procedures. Only investigators/research team affiliated with CCHMC will have access to secured files and/or research data and will be well-informed regarding the protection of participants' rights to confidentiality.

As the randomization and "dispensing" of the intervention is conducted via software, investigators, study staff, and study subjects will all be blinded to the randomized study treatment assignments.