First block of re-extinction showed significantly increased freezing compared with the last block of extinction (P<0.05). Consistent with the ongoing Treatment effect at extinction and re-extinction, young mice froze less overall than aging mice (*P<0.05 main effect of Treatment with significant post-hoc differences). Reminder and Sex had no effects. Males (young standard no shock = 7, young standard shock = 6; aged standard no shock = 7, aged standard shock = 9; aged running no shock = 8; aged running shock = 4) and females (young standard no shock = 7, young standard shock = 8; aged standard no shock = 7, aged standard shock = 7; aged running no shock = 7, aged running shock = 7).