Figure 1.

Examples of stimuli used in different conditions. All environments had five structural elements (walls or towers). There were five levels of boundary, from zero to four walls. There were four levels of color, aimed to be of increasing complexity to imagine. No behavioral measures differentiated the levels mixed (1) and mixed (2) so these were combined for the imaging analyses. Subjects were asked to imagine standing on the central yellow dot and visualizing the environments from this location. After forming a clear mental image facing a self-selected direction, they were required to then imagine rotating through 360°.