GRM1 and fragile X syndrome: Notably, the specific aspects of group I mGluR function we validate as occurring in human cortex are also dysregulated in mouse models for FXS, notably enhanced LTD in hippocampal pyramidal neurons (Bear et al., 2004) and altered GABAergic inhibitory function specifically mediated by mGluR1 (Paluszkiewicz et al., 2011a; Cea-Del Rio and Huntsman, 2014).