Neurophysiologic Biomarkers in Rett Syndrome

The goal of this observational study is to identify candidate biomarkers in individuals with Rett Syndrome (RTT). The main questions it aims to answer are: * Do these biomarkers change during clinical changes in individuals with RTT? * Are biomarkers stable over time in clinically stable individuals? * Do these biomarkers correlate with severity of RTT? Participants will be asked to undergo an electroencephalogram (EEG) with measurements of Evoked Potentials (EP) to measure electrical activity in the brain. Researchers will compare findings in individuals with RTT to those in typically developing individuals to see if there are differences between the two groups.