Figure 1.

Cross-modal sensory preconditioning. A, Schematic diagram of the experimental setup. Tethered flies can control their orientations relative to visual cues or odors by generating yaw torque, which was measured with a torque meter and used to control the panorama rotation. The visual cues were horizontal bars with 30° separation of elevation. The odors were 0.99% 3-octanol (OCT) and 0.99% 4-methylcyclohexanol (MCH). B, Top, Time course of cross-modal SP. Individual Canton-S flies were subjected to paired visual and olfactory cues in the pretraining session (V + O), followed by unimodal visual conditioning (V). The paired cues were presented to the flies again as a reminder, and the olfactory cues (O) were tested after a 4 min dark period. The Test 2 PI (averaged in the right panel) was significantly positive (p < 0.001) after the visual and olfactory cues were explicitly paired in time, but was not significantly different from zero after presenting the unpaired cues. C, Similar to B, but flies were trained with olfaction and tested with vision. D, The random spots did not interfere with olfactory conditioning. The flies were subjected to normal odor delivery, no odor, or reversed odor delivery in the last 6 min of the protocol. Top, Time course of unimodal olfactory conditioning. Bottom, The averaged PIs of the Test 2 section (block 10–12). E, The random spots did not interfere with visual conditioning. The flies were subjected to a 4 min dark interval (D, dark) followed by a 4 min period with no visual cues (B, blank) and visual cues (V) again, in the test session. Data are presented as means ± SEM. n indicates the total number of flies examined. ***p ≤ 0.001.