Figure 11.

Characteristics of head drifts among CD patients attempting to aim the head at an LED target with or without a head-fixed laser. The amplitudes (A) and the frequencies (B) of cycles without the head-fixed laser are plotted on the y-axis while those with the head-fixed laser are plotted on the x-axis. Each data point represents one patient. Dashed line is an equality line. All data points depicting amplitude fell above the equality line, indicating significantly larger drift amplitudes without the laser (paired t test, p < 0.01). Data points representing frequency fell below the equality line, demonstrating a significantly lower frequency without the laser (paired t test; p < 0.05). The relationship between head amplitude and velocity of head movements is shown in C. Black symbols show the condition without the laser while open symbols show the condition with the laser. Visually guided head saccades from the same patients are shown in gray. The data from both sources overlapped suggesting similar kinematic properties.