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. 2001 Mar 13;98(6):3537–3542. doi: 10.1073/pnas.051630498

Figure 1.

Figure 1

Schematic representation of one cycle of the shuffling procedure (condition 2). The circular arena consists of a rotatable inner disk and an immobile peripheral belt (DISK and BELT). (A) As long as the rat is on the inner part of the arena, the disk slowly rotates (solid arrow) together with the shock sector (zigzag arrow), the rotation of which is indicated by a dashed arrow. The outer part of the shock sector projects to and moves over the stationary belt. The arena surface forming the original location of the shock sector is painted gray. The rat moves from a central part of the arena to the opposite circumference, but the room frame TV camera sees the active locomotion along a radius combined with counterclockwise rotation of the disk as a spiral. (B) When the rat approaches the disk–belt border and enters the “transition zone” (denoted by dotted concentric circles), rotation of the disk stops. Note that the punished part of the floor remains the same on the disk but is on a different part of the belt. The radial direction of the track is seen as radial. (C) After the rat moves from the transition zone into the outer belt, the disk resumes rotation again (solid arrow), but the punished sector, anchored to the stationary belt, is projected to new areas of the disk surface. The track on fixed belt is seen undistorted. (D) Rotation of the disk stops when the animal returns to the transition zone (dotted circles). Note that at this moment the position of the shock sector on the disk has moved to a different part of its floor. The track through the transition zone is undistorted. The return of the rat to the inner disk marks the end of one complete cycle of shuffling and restores the situation shown in A. (E) Computer-reconstructed locomotion of the rat in the substratal idiothetic frame as seen with a virtual TV camera rotating with the disk, when the rat was on the rotating disk, and as seen with the real camera, when the rat was on the belt or on an immobile disk. Note that the shock sector always remains in the idiothetically correct position with respect to the rat, but the floor areas (dark gray), originally corresponding to the prohibited sector, are dispersed over the arena surface.