Figure 1.

Main task and types of trials. A, Schematically depicts the allocentric position discrimination task (main task). The red spot indicates the central fixation point, which remains visible throughout the trial. Subjects were required to fixate at it throughout the trial. After a random delay (600–1000 ms), the visual cue composing of two green dots (one small and one big) appeared at one of 8 egocentric locations. Subjects needed to press either the left key or the right key, based on the relative position of the bigger dot (target) to the smaller dot (reference). B, Based on the ego- and allocentric representations of the target, trials could classify into two groups (compatible, incompatible). Compatible: egocentric left and allocentric left (LL), or egocentric right and allocentric right (RR); incompatible: egocentric left but allocentric right (LR), or egocentric right but allocentric left (RL).