FMR1 and fragile X syndrome: Previously, we reported that Fmr1−/− mice, the best-studied animal model of FXS (Dutch-Belgian Fragile X Consortium, 1994), exhibit impairments on a go/no-go visual discrimination task compared with wild-type (WT) controls—a deficit that was recapitulated in humans with FXS (Goel et al., 2018).