Fig. 4. Cognitive function assessed with trace fear conditioning. Seven-day-old rat pups that received no treatment (naive control), 70% N2O + 0.75% isoflurane (N2O + ISO), 70% xenon, 70% N2O, and 8% oxygen (hypoxia) preconditioning followed by N2O + ISO, and they were then allowed to live up to the age of 40 days for cognitive function test. (A ) The mean data of percentage of freezing time after context testing. (B ) The mean data of percentage of freezing time after tone testing. (C ) The average data of the area under curve (AUC) derived from (B ). Mean ± SD, n = 6. *P < 0.05 versus naive.