We used wild type Canton S and radish mutant Drosophila flies as in van Swinderen & Brembs (2010). However, the genetic background was now changed to the Canton S strain of Thomas Préat, to test for the stability of the effect across genetic backgrounds. Flies were tethered as described previously (Maye et al., 2007) and tested the following day for flight behavior (for a video of the procedure, see Brembs, 2008). The duration of the experiments had to be confined to 6 min because radish mutants were reluctant to fly continuously in the arena, sampling rate 20Hz. In this experiment, four identical stripes were placed in the center of the four quadrants on the wall of a cylindrical drum. The fly was placed in the center of that drum, attached to a torque meter. The angular speed of arena rotation was made inversely proportional to the yaw torque signal of the fly (Dill et al., 1993; Brembs and Heisenberg, 2000, 2001). Power spectra were computed from the yaw torque data. The 3-6h Methylphenidate ("Ritalin") treatment was administered directly before the experiment at a concentration of 0.5 mg/ml in a 5% sucrose solution.