Tilt of angular eye velocity rotation planes during straight-line tracking.

<p>(<i>A</i>) Rotation plane tilt angles of total (Ω_eye) and Donders-Listing (Ω_DL) angular eye velocity during horizontal tracking in 15° gaze down, plotted across one oscillation cycle (5 response cycles superimposed, Ω_eye: black traces, Ω_DL: gray traces). (<i>B</i>) Rotation plane tilt of Donders-Listing angular velocity as a function of estimated target distance relative to straight ahead (data from 5 cycles). Note the small but steadily increasing deviation of tilt angles from the half-angle slope relation (dashed line) with increasing estimated target distance (least-squares fitted line through target positions: slope = 0.49, offset = 0.2°). (<i>C</i>) Average ratios of rotation plane tilt angles of Donders-Listing angular velocity to estimated target distance as a function of estimated target distance relative to straight ahead. Each of the data points was obtained by least-squares fitting tilt angles versus estimated target distance, collected in 5°-wide intervals across the range of 0° to 25°.