The MK801-induced long-term memory impairment coincides with a significant impairment of IEG induction in RSC 30 mins after training (two-way interactions: Fos F (1, 28) = 10.98, p < 0.01; Arc F (1, 28) = 6.06, p < 0.05; Npas4 F (1, 28) = 25.28, p < 0.0001; contrast: p < 0.01 for all three genes in MK801 vs. vehicle treated trained mice; Fig. 3c), as well as in HC (interactions: F (1, 20) = 6.01, p < 0.05;; Arc F (1, 20) = 3.86, p = 0.06; Npas4 F (1, 20) = 8.11, p < 0.01; contrast: p < 0.01 for all three genes; Fig. 3d). Here, NPAS4 is linked to memory impairment.