GRM5 and Cognitive impairment: Subsequently, preclinical studies examining several first generation full mGlu5 NAMs including MTEP and fenobam reported sedation, psychotomimetic-like effects, and cognitive impairments (Kinney et al., 2003; Homayoun et al., 2004; Jacob et al., 2009; Abou Farha et al., 2014; Gould et al., 2015).