Figure 2.

Time requirements for synaptic output from MBN subsets for the retrieval of aversive olfactory memory. A, All flies were trained using an aversive unconditioned stimulus at 24°C and shifted to 32°C 10 min before a retrieval test. A synaptic blockade imposed by the expression and activation of shi^ts in the α′/β′ MBNs significantly reduced memory expression from 15 min to 1.5 h after training (Mann–Whitney pairwise comparisons, p ≤ 0.0043). No significant difference was observed during retrieval of memory at 3 or 24 h after training (Mann–Whitney pairwise comparisons, p ≥ 0.4452). A small decrement in expression of aversive memory was observed during retrieval at early time points at restrictive temperature in control flies carrying only the c305a-gal4 element (Mann–Whitney pairwise comparisons, p ≥ 0.0022) due to heat stress. This decrement was not observed at subsequent time points (Mann–Whitney pairwise comparisons, p ≥ 0.0931) and is discussed further in the text. B, Synaptic blockade of γ MBNs significantly reduced aversive olfactory memory expression from 15 min to 3 h after training (Mann–Whitney pairwise comparisons, p ≤ 0.0260). No significant difference was observed during retrieval of memory at 24 h after training (Mann–Whitney pairwise comparison, p = 0.4286). A small decrement in performance of aversive memory was observed during retrieval of 15 min to 1.5 h memory at restrictive temperature in control flies carrying only the 1471-gal4 element (Mann–Whitney pairwise comparisons, p ≥ 0.0152). This impairment was not observed at subsequent time points (Mann–Whitney pairwise comparisons, p ≥ 0.6623). C, Synaptic blockade of α/β MBNs significantly reduced aversive olfactory memory expression from 15 min to 24 h after training (Mann–Whitney pairwise comparisons, p ≤ 0.0095). A small decrement in performance of aversive memory was observed during retrieval at 15 min and 1 h at restrictive temperature in control flies carrying only the c739-gal4 element (Mann–Whitney pairwise comparisons, p ≥ 0.0411). This impairment was not observed at subsequent time points (Mann–Whitney pairwise comparison, p ≥ 0.1320). D, A slight decrement in performance of aversive memory expression was observed during retrieval from 15 min to 1.5 h at restrictive temperature in control flies carrying only the uas-shi^ts genetic element (Mann–Whitney pairwise comparison, p ≥ 0.0303). This impairment was not observed at subsequent time points (Mann–Whitney pairwise comparison, p ≥ 0.3095).