The Problem of Over Completeness

• We have seen that the eye muscles and brainstem neural circuits have a capacity to rotate the eye in 3 dimensions.
• To point the fovea at an object is a 2 dimensional problem, it can be done with only vertical and horizontal rotations.
• Thus the brain has a choice of final positions (A or B or C).
• Donders found that the brain always made the same choice (i.e. B, not A or C).
• This property is called Donders' law.