A) Behavioral findings from the context fear test show that PD 24 fear conditioned subjects froze significantly more in the context than PD 17 fear conditioned subjects. B) Fos mRNA levels in the amygdala, hypothalamus, hippocampus and perirhinal cortex following the context fear test in PD 17 and PD 24 subjects. One-way ANOVAs for condition and age reveal effects of context exposure on Fos levels in all four regions, while age differences were found in all regions except the hypothalamus. C) Egr1 mRNA concentration in the amygdala, hypothalamus, hippocampus and perirhinal cortex following the context fear test. One-way ANOVAs for condition and age reveal significant effects of condition in the PD 17 hypothalamus and hippocampus, and the PD 24 perirhinal cortex. Effects of age were found in the tone-alone condition in the hippocampus and both tone-alone and fear conditioned groups in the perirhinal cortex. Different from home cage: * = p<.05, + = p<.10; Different from tone-alone: λ = p<.05; Different from fear conditioned: ^ = p<.05; All other differences: # = p<.05