GRM5 and memory impairment: Despite encouraging results, both clinical and preclinical studies suggest that mGluR5 NAMs may induce on-target adverse effects, including cognitive and memory impairments and psychotomimetic effects (Campbell et al., 2004; Porter et al., 2005; Rodriguez et al., 2010; Abou Farha et al., 2014), raising the question of whether complete blockade of mGluR5 may contribute to these deleterious effects, thereby limiting the therapeutic utility of mGlu5 NAMs.