GluN2B subunit activity within the ACC is necessary for trace fear learning. (A) Mice exposed to bilateral 0.5 μl infusions into the ACC of either Ro25-6981 (2 μg/μl) or saline 15 minutes prior to trace fear training exhibited similar learning curves. (B) Mice exposed to Ro25-6981 prior to training showed a significant reduction in freezing behavior in response to the CS when tested in a new context 48 h later (saline: n = 4; Ro25-6981: n = 4, t = 3.06). (C) (Left) The memory impairment was still evident one month after training. (Right) Representative markers indicating microinjection locations. (* P < 0.02 ).