Fig. 6.

Fear conditioning 4 months after 4 h of isoflurane (iso) anesthesia (n = 13) or sham anesthesia (control, n = 11) administered to 16-month-old rats. Unconditioned fear is measured by freeze scores at baseline before (A) and 24 h after exposure to the conditioned stimulus–unconditioned stimulus pairings (B). The time curve (C) and summary (D) of the tone test reveals no difference between groups in the degree to which the nonhippocampal-dependent association between the tone and the foot shock were formed. During the hippocampal-dependent context portion (E and F) of the test, there was also no difference in freeze scores between groups (P > 0.24, Mann–Whitney U test).