Figure 3.

The Appetitive Memory Trace of the DPM Neuron Defines the Time Window Over Which Synaptic Transmission is Required for Normal Appetitive Memory.

(A) Schematic illustration of the conditioning protocols with temperature shifts that were used for these experiments. All flies were trained at the permissive temperature (21°C) and then shifted to restrictive temperature (32°C) for the times indicated. Retrieval tests were all performed at 21°C at 3 or 6 hr after training and a Performance Index (PI) calculated. The letters (B–E) at the left side of the illustration are a cross-reference to the data panels B–E. For reasons that are unclear, the uas-shi^ts/+ genotype often performed at higher levels than the c316-gal4/+ control or the experimental genotype under permissive conditions. However, the relevant comparisons are within-genotype and between temperatures.

(B) Flies were trained using the appetitive protocol at 21°C, transferred to 32°C immediately after training and returned to 21°C after 1 hr. Blocking DPM synaptic transmission across this time window significantly reduced 3 hr appetitive memory (Mann-Whitney pairwise comparison, p=0.041) for the experimental group. No significant difference was observed between permissive and restrictive temperatures for control groups (Mann-Whitney pairwise comparisons, p≥0.4557).

(C) Flies were trained using the appetitive protocol at 21°C, transferred to 32°C at 1 hr after training and returned to 21°C after 2.5 hr. Blocking DPM synaptic transmission across this time window significantly reduced 3 hr appetitive memory (Mann-Whitney pairwise comparison, p=0.0041) for the experimental group. No significant difference was observed between permissive and restrictive temperatures for control flies (Mann-Whitney pairwise comparison, p≥0.3939).

(D) Flies were trained using the appetitive protocol at 21°C, transferred to 32°C immediately after training and returned to 21°C after 2.5 hr. Blocking DPM synaptic transmission across this time window nearly abolished 3 hr appetitive memory (Mann-Whitney pairwise comparison, p=0.0022) for the experimental group. The performance of c316-gal4/uas-shi^ts flies at the restrictive temperature was significant different from zero (Wilcoxon signed rank test, p=0.0156). No significant difference was observed between permissive and restrictive temperatures for control flies (Mann-Whitney pairwise comparison, p=≥0.5887).

(E) Flies were trained using the appetitive protocol at 21°C, transferred to 32°C at 4.5 hr after training and returned to 21°C before testing. Blocking DPM synaptic transmission from 4.5 to 6 hr after training did not alter 6 hr appetitive memory (Mann-Whitney pairwise comparison, p=0.6991). No significant difference was observed between permissive and restrictive temperature for control flies (Mann-Whitney pairwise comparison, p=≥0.6991).

(F) Flies were trained using the aversive protocol at 21°C, transferred to 32°C 1 hr after training and returned to 21°C after 2.5 hr. Blocking DPM synaptic transmission from 1 to 2.5 hr after training did not impair 3 hr aversive memory (Mann-Whitney pairwise comparison, p=0.2786) for the experimental group. No significant difference was observed between permissive and restrictive temperature for control flies (Mann-Whitney pairwise comparison, p≥0.5737). Error bars indicate the standard error of the mean. n=6–8 for all groups. See also Figure S2.