FMR1 and fragile X-associated tremor/ataxia syndrome: Third, both COP variability and complexity alterations in FMR1 premutation carriers were associated with higher CGG repeats and ICARS-rated posture, gait, and motor deficits, suggesting that our measures may provide sensitive and highly quantifiable biologically based markers of behavioral and neurological features associated with FXTAS risk or progression in premutation carriers (Fig. 2).