GRIN1 and Mental deterioration: On the other hand, spine density reduction is induced by GluN1 knockdown in the pyramidal neurons.96,140,141 Spatial reference memory in Morris water maze test is intact in PV-cre/GluN1 KO mice112 but is severely impaired in αCaMKII promoter-driven GluN1 knockout mice.101 It is plausible that cognitive decline observed in a subtype of chronic patients may be explained by NMDAR hypofunction in cortical pyramidal neurons.