Figure 6. Ndufs4 cKO mice are deficient in contextual fear memory extinction.

(a) Control and Ndufs4 cKO mice have similar levels of contextual fear memory 24 h post-training. (b) Control and Ndufs4 cKO mice showed similar cued-fear response 24 h post-training. (c) Neither control nor Ndufs4 cKO mice froze when placed in a novel context 24 h after training. (d) However, fear extinction was impaired in Ndufs4 cKO mice. (e) The freezing response that persisted in Ndufs4 cKO mice after 8-days of fear extinction training was context specific because the mice did not freeze in a novel context after fear extinction trials. **p < 0.01.