FMR1 and fragile X syndrome: We were interested in the mGluR-dependent LTD because its involvement in synaptic pathophysiology has been confirm in two syndromic forms of autism with intellectual disability, tuberous sclerosis complex (TSC1+/-, TSC2+/-) and fragile X syndrome (Fmr1-/-; Bear et al., 2004; Zoghbi and Bear, 2012).