Fig. 1.

Representative examples of combined movements to a target of 90° offset. The panels above show a cartoon with the successive target presentations and head/trunk positions adopted before and after outbound and inbound turns. Left panels show recordings of a leftward outbound (non predictable) turn in a patient (black traces) and a control subject (gray traces) for comparison. Right hand records show traces of the patient’s rightward (inbound) turn to the central target. Displacement signals are displayed at the top and velocity signals at the bottom. The primary gaze shift in the patient (between dotted vertical markers) fell short of the target and more than 50 % of the visual angle in the patient was covered by the sum of fast nystagmic phases and head motion in space. In contrast, the primary gaze shift executed by the control covered approximately 80 % of the target eccentricity. Acquisition time is defined between the onset of the primary gaze shift and target fixation (for the patient indicated by the length of horizontal arrows). The oblique bold arrow shows an involuntary head-on-trunk dystonic movement which does not interfere with the execution of the inbound voluntary turn