Fig. 1.

Experimental apparatus and procedure. Photograph (A), schematic illustration (B), and functional diagram (C) of the Servoball setup. A 60-cm sphere (treadmill, 1) rests on a multidirectional roller system (2 and 4). The sphere is rotated by two orthogonal feedback-controlled position servos (2 and 3). The 2-dimensional position of the freely moving animal is sensed by infrared (6) high-speed video (5). Animal movement is restricted by a Perspex glass cylinder (7), which is moved up and down by a servomotor (8). VR is presented on eight peripheral TFT monitors (9). Four loudspeakers (10) are located above the cylinder. Retractable liquid feeders (11) are integrated beneath the cylinder. D–F: animal management system: individual sorter (D), home cage with food supply (E, 17), sorter, Servoball arrangement (E) with functional diagram (F). 14–16: ID sensors; 12 and 13: gates; 18: tunnel giving access to the Servoball. See methods for a description of the individual gating procedure. A: the photograph placed on the backside of the monitor ring shows a view into the system with a rat. VR, virtual reality.