Evidence of synapse malfunction came from studies on the Fmr1 gene knockout (Fmr1 KO) mouse, an animal model of FXS that displays typical features resembling those of FXS patients, among which alterations in dendritic spine morphology (Comery et al., 1997; Nimchinsky et al., 2001) increased susceptibility to audiogenic seizures (Musumeci et al., 2000) and cognitive impairment (Bernardet and Crusio, 2006; Dolen et al., 2007). Here, FMR1 is linked to fragile X syndrome.