Depiction of experimental remote-controlled visual stimulus delivery and tracking systems.

<p>(A) To examine the turtle's visual obstacle recognition, an experimental arena was equipped with a camera and two movable cylinders as obstacles (shown from the side view and from above). The dimensions of the arena, surrounding walls, and obstacles are indicated. (B) Experiments performed on the laboratory floor area (with the dimensions indicated) are shown in the drawing. The placements of the turtle, obstacle, and tracking system are shown. (C) The embedded control system to block the turtle's view is shown in the drawing. The servo motor controls the positioning of the semi-cylinder obstacle (in the image, it is positioned directly in front of the turtle). The red circle on the controller tracked by the simple tracking algorithm was regarded as the location of the turtle. (D) The turtle was remotely controlled to follow the desired path by alternating the visual angle of the obstacle between ±180 (no stimulus) and ±90 degrees (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0061798#pone.0061798.s001" target="_blank">Movie S1</a>).