Mean (± SEM) percent of freezing by CRND8 mice and their non-transgenic (nTg) littermates at three, six, and 12 months of age. (A) CRND8 mice showed significantly lower rates of freezing as compared to nTg mice immediately following the presentation of a foot shock during training (P < 0.001 - genotype effect). (B) Overall, the context memory of CRND8 mice was impaired as compared to control nTg mice (P < 0.01 - genotype effect). No differences in context memory were found between nTg and Tg mice at three and six months, but at 12-months the CRND8 mice were significantly impaired (post-hoc Bonferroni t-test). (C) CRND8 mice froze significantly less than nTg mice during the pre-tone (left panel) and the tone (right panel) phases of the test. The CRND8 mice showed significant impairment in tone fear memory at each age of testing (right panel). Three, six, 12 on the abscissae refer to the age of testing. * P < 0.02, ** P < 0.01, *** P < 0.001.