Figure 5.

Classic conditioning in the flight simulator with normal (b,c) and HU-treated, MB-less flies (d). During training (a), the flight simulator mode is switched off. Two stable pattern orientations are presented to the fly (upright or inverted T in frontal position) and are interchanged every 3 sec (displacement period, 220 msec). With one of the pattern orientations heat is on (top) and with the other it is off (top). This procedure is repeated continuously during the entire training period of 4 min. The two 2-min preference tests as well as the learning tests are performed operantly in the flight simulator mode. During tests, PI is evaluated as PI = (t_a − _b)/(t_a + t_b) (see Fig. 2), except that here t_a and t_b indicate the time during which flight is directed toward a narrow sector of ±3°C around the center positions of the patterns. During training, t_a = t_b, therefore, PI is zero (gaps between preference tests and first memory test, and between first and second memory test in b–d). In c the arena illumination is switched off during the 220 msec of pattern displacement to present only retina-stabilized images during training (see text for further explanations). Eliminating the pattern movement and introducing the “dark flashes” has no significant effect on preference and memory scores (for PIs of first memory tests, P > 0.05; of the final memory tests, P > 0.1). (d) As already established in the operant conditioning experiments (Figs. 2–4), HU-treated MB-less flies learn and remember as well as the controls in b. Error bars are s.e.m. for the number (n) of flies.