In this study the investigators aim to identify and characterize a potential neurophysiological biomarker by mapping functional networks of brain activity (Brain Network Activation, BNA) based on analysis of evoked response potential (ERP) signals in both asymptomatic FMR1 premutation carriers and in patients with various stages of FXTAS. Additionally correlations will be studied between these BNA scores and demographics (gender, age and disease duration) as well as genetic mutation and clinical scores.