Extended Data Fig. 2: Rats in our NpHR learners group showed a persistent increase in conditioned fear to the contextual cues, which extinguished before tone presentations in the extinction test.

During conditioning, our NpHR learners group showed high levels of fear to the background contextual cues (left; see Fig. 3 in main text for more information). To reduce these levels of context fear before the test, 24 hours after conditioning, rats received a context extinction session where they were placed in the experimental chambers without any stimuli. Here, we found that our NpHR learners group maintained higher level of context fear relative to our eYFP learners group (middle). This context extinction was effective in reducing contextual fear as all rats showed low levels of freezing at the beginning of the next test session, where we presented the tone under extinction to examine fear that had acquired to these stimuli (right). A mixed-design repeated-measures ANOVA on levels of freezing to the contextual cues across the context and tone extinction sessions showed a main effect of time (F_14,140 = 4.614, p = 0.000), and a significant session x time x group interaction (F_14,140 = 1.697, p = 0.032). This interaction was owed to a between-group difference in freezing during context extinction that revealed itself most prominently towards the end of the scoring period (group: F_1,10 = 5.939, p = 0.035), that was not seen in the tone extinction test (group: F_1,10 = 0.007, p = 1.000). Further, there was a significant difference in freezing exhibited by the NpHR group when comparing the context extinction session with the tone test (n = 6 rats; F_1,10 = 8.071, p = 0.018), that was not present in the eYFP control group (n = 6 rats; F_1,10 = 1.161, p = 0.307). Finally, a one-way ANOVA showed there was no between-group difference in freezing to the context immediately before tone presentations in the tone test after context extinction had taken place (F_1,10 = 1.943, p = 0.194). Error bars = SEM.