Alterations of Eye Movement Control in Neurodegenerative Movement Disorders

Figure 4

Videooculographic recordings depicting an upward visually guided reflexive saccade elicited in a sudden target jump ranging from −15 to +15 degrees in a patient with progressive supranuclear palsy (PSP, left panel) compared with an age-matched healthy control (right panel). The PSP patient reaches the target (dashed line) in a pathological multistep pattern, approximately 2.5 seconds (𝑥-axis) after new stimulus appearance (black line, vertical gaze position, and 𝑦-axis) whereas the control’s gaze shift is accomplished after about 600 milliseconds. Abnormal horizontal square wave jerks (SWJ) manifest in the orthogonalized horizontal eye position (gray line in the left panel), together with vertical saccades indicating a curved trajectory. In contrast, the horizontal eye position in the control subject (gray line in the right panel) exhibits no alteration. The lower row shows the corresponding vertical eye velocity (𝑦-axis) computed by use of sample-by-sample differences of the vertical eye position signal. The PSP patient (left) fails in generating larger saccades resulting in a reduced peak eye velocity (PEV) compared with the control subject.