Finding the Way with a Noisy Brain
Figure 1
Illustration of simple directed walks.
(A) An allothetic directed walk (ADW) occurs when the navigating agent measures current heading directly from an external reference (a compass, represented here as a sun). Following each step, the agent is able to reorient itself to the desired compass direction. (B) An idiothetic directed walk (IDW) occurs when the navigating agent estimates current heading by integrating rotations, often estimated from internal cues. Without a compass, the agent cannot reorient itself following each step. The illustrative animal is an arthropod consisting of a head, thorax (assumed to be the point-position of the animal for illustrative purposes), and abdomen. In both cases, the animal intends to take three steps away from home (red rectangle) ideally along a straight line (intended locomotion), but due to cumulative sensorimotor noise, moves along the actual trajectories as shown. For illustrative convenience, the sun is aligned with the direction of intended locomotion, which is designated the X-axis in the text. See text for further details.