Figure 3. Following training flies exhibit a persistent search bias in the absence of the cool tile and retain this memory for several hours.

Flies are tested in a probe trial (#11) where the visual display is relocated but no cool tile is present. (a) Trajectories from four representative flies, each plotted for 60 s after leaving their starting quadrant. Flies start in the top-left quadrant (Q1, Start); the dashed square denotes the “expected” location of the cool tile (Q2, Target). (b) Flies preferentially search in the quadrant where they have been trained to find the cool spot (Q2), even when the cool spot is absent; values are mean ± SEM, n=33 experiments, 495 flies. (c) Probe learning index is significantly greater than zero (indicating learning) when flies are trained with a coupled visual panorama (red, p<0.0001, n=33), but not when trained with an uncoupled (grey, p=0.28, n=21) or dark (black, p=0.39, n=23) visual panorama. (d) To test place memory retention, flies were tested in a probe trial at several time intervals following training (n≥5). Flies retain visual place memories for at least 2 hours after training. Box plots indicate the median value (solid black line), 25 and 75 percentiles (box), and the data range (dashed whiskers). For details of calculations and additional statistics, see Methods.