FXR2 and fragile X syndrome: Moreover, in a mouse model of fragile X syndrome (FXS; dfmr1 and Fmr1 knockout (KO)/Fxr2 heterozygote) where circadian rhythmicity is affected, interictal epileptiform discharges (IEDs) appear in the EEG, indicating a common dysregulation of the balance between inhibitory and excitatory tone in cortical computations [123, 124].