For example, in mouse fmr1 knockout models of fragile X syndrome, immature spine morphologies have been described in several brain areas, including the cortex (Comery et al., 1997; Cruz-Martín et al., 2010; Nimchinsky et al., 2001; Pan et al., 2010), hippocampus (Grossman et al., 2006), cerebellum (Koekkoek et al., 2005) and amygdala (Qin et al., 2011). This evidence concerns the gene FMR1 and fragile X syndrome.