Oculomotor control: Listing's law and all that.

Previously, eye positions were characterized by the direction of sight, which has two degrees of freedom for conjugate movements and three degrees of freedom for vergent movements. Several groups have recently presented reliable data and unconventional models on binocular coordination, where all three degrees of freedom for one or both eyes have been taken into account. The results illustrate Bernstein's principle that in order to simplify control, the brain establishes unique relations between the target and motor space, in which non-Euclidean geometry of rotations is observed.