Fig. 4

The % freezing values to the tone during fear conditioning phase 1 at 12 weeks of age and fear conditioning phase 2 at 90 weeks of age. All data points are the means±SEM. **/##p＜0.01 indicates a statistically significant difference from the first trial of fear conditioning in 12 weeks old group/90 weeks old group. ††p＜0.01 indicates a statistically significant difference between the 12-week-old and 90-week-old mice.