Figure 2.

State space portraits of the memory network. Biological realizations of line attractor dynamics are inevitably imperfect, and are accompanied by various types of systematic eye position drift. In all cases, the trajectory along the oblique axis is very slow, and looks like a line of fixed points on short time scales. (A) Point attractor, corresponding to centripetal ocular drift to a null position. (B) No fixed points, corresponding to unidirectional ocular drift and no null position. (C) Saddle point, corresponding to centrifugal ocular drift. (D) Several point attractors spaced along a line, corresponding to multiple null positions.