Figure 4.

(A) Percentage of conditioned responses (CRs) on session 1 in mice aged 4 (n = 8), 12 (n = 8), and 18 (n = 8) months over 10 nine-paired trial blocks in the 250-msec delay eyeblink classical conditioning procedure as assessed by computer scoring of CRs. Block-by-block CR acquisition on the first day of training reveals that older mice acquire CRs considerably more slowly than do young mice. (B) Percentage of CRs on session 2 in the same mice over 10 nine-paired trial blocks in the 250-msec delay eyeblink classical conditioning procedure as assessed by computer scoring of CRs. The second day of acquisition shows that age-related differences in percent CR do not extend beyond the first training session.