Figure 5

KO mice showed normal STM and a defect in LTM and in the process from recent to remote memory. a, Acquisition of freezing responses during the training trial. Three footshocks (arrows) were administered in a conditioning chamber. The mean percentage of time spent in freezing is plotted per 1 min. b, Average freezing during the last 3 min of the training session (P = 0.43, t test). c, Experimental design and conditioned freezing responses 1 h after the training. The mean percentage of time spent in freezing during the 6 min test session is plotted (P = 0.39, t test). d, Experimental design and conditioned freezing responses 24 h after the training. During the training session, mice received either 3 or 5 footshocks. e, Experimental design and conditioned freezing responses. Mice received 5 footshocks and freezing responses were assessed for 6 min at the test day indicated. No significant differences in freezing responses were detected, with the exception of the 32-day test, in which KO animals showed a decreased freezing response when compared with WT mice. The number of mice used for each experiment is indicated in the graph. Note that different groups of mice were used for each experiment. *, P < 0.05, t test.