 Now, we're going to show you an example of a patient with progressive super-nuclear palsy. Look here in forward gaze. All of these psychotic intrusions are not in a stagmus. They're actually square wave jerks. There's a fast phase that takes the eyes off of the target and another fast phase that brings the eyes right back to primary fixation. This differs from the stagmus, which have an initial slow phase. These are actually psychotic intrusions. This pursuit is a little psychotic. It's not smooth. Now we're going to show you psychods. Little slow, little inaccurate. But again, you can see fixation is disrupted by these continued square wave jerks, these psychotic oscillations. They're called oscillations when they're relatively continuous and intrusions when they're intermittent. Now here we're showing that the patient with dals head maneuver actually has a fairly full vertical movement of the eyes as opposed to saccades in pursuit.