Article Figures & Data
Figures
- Fig. 1.
Typical examples (subject MF) of head and right eye velocities elicited by a rightward pulse of head acceleration starting at time 0. A: 10 subsequent individual pulses superimposed to show noise level and variability within a measurement. Eye velocity has been inverted for easy comparison with head velocity.B: mean ± SD (vertical gray bars) of 23 similar rightward rotations in the same measurement as in A.Such averages from a measurement formed the basis of all subsequent analysis. Linear regressions on head and eye velocity over a range of 10–50°/s are shown. Visual condition: 1 light-emitting diode (LED) at 220 cm distance extinguished 50 ms before head movement.
- Fig. 2.
Distributions of acceleration gains derived from linear regressions (slope eye velocity/slope head velocity) for a far target (A), a near target (C), and darkness (E). Pooled results from 6 subjects, 2 eyes, 2 directions, and (for A and C) 3 visibility conditions of targets (extinguished at −50 or −500 ms or left on). Differences between the gains of the ipsilateral and contralateral eyes (relative to the direction of rotation) are shown inB, D, and F. The difference is statistically significant only for the near target.
- Fig. 3.
A: distribution of vestibulo-ocular reflex (VOR) latency for the contralateral and ipsilateral eyes estimated from linear regressions on eye and head velocity. Pooled data of 6 subjects, 7 visual target conditions, and 2 directions. B: distribution of the difference between the latency of the ipsilateral and contralateral eyes.
- Fig. 4.
Speed profiles of the head and the contralateral and ipsilateral eyes. Pooled data of 6 subjects, 7 conditions, and 2 directions (here normalized to rightward) showing the average latency difference between the eyes.
- Fig. 5.
Scatter plots of latency and gain as a function of the absolute value of the maximum anti-compensatory velocity. Pooled data for 6 subjects, 2 directions, 2 eyes, and 7 conditions (distant or near target and darkness). A: latency estimates showing the apparent increase in latency as a function of increasing anti-compensatory speed. The two separate linear regressions were calculated for the data representing the contralateral and ipsilateral eyes. B: similar tendency for acceleration gain to increase with increasing anti-compensatory velocities. Three separate linear regressions were calculated for far and near targets and darkness. The crosses represent model data, as described in Isolation and modeling of the passive eye movements.
- Fig. 6.
The mechanical relations of the eye and its surrounding tissues in the orbit. A: the emergence of a linear acceleration of the orbit as a result of eccentric rotation. B: a semi-solid gel in a rigid vessel as the mechanical analogue of the tissues in the bony orbit. A linear acceleration parallel to the free surface causes a deformation that corresponds to an anti-compensatory rotation.C: a dummy experiment with eccentric rotational acceleration of the device in B instead of a subject's head. Coils were attached to the bottom of the vessel (“head”) and the free surface (“eye”). The eye velocity was initially anti-compensatory; subsequently it oscillated.
- Fig. 7.
A: reconstruction (using real data) of the passive mechanical eye response by subtracting a theoretical active VOR with a gain of 1 and a latency of 8 ms from the recorded eye movement. The result is an initially anti-compensatory eye velocity that is followed by oscillation (qualitatively resembling Fig. 6 C).B: the passive mechanical response, expressed in angular position, obtained by integrating the reconstructed mechanical velocity response in A. C and D: as in A and B, but for model data simulating the eye movements as the sum of a passive and an active component, as described in Isolation and modeling of the passive eye movements.
- Fig. 8.
A: instantaneous velocity and acceleration gains in a typical subject, calculated with due accounting for latency, i.e., Gaint = Veyet /Vhead(t−latency). Notice the steep rise above unity and subsequent oscillation of the acceleration gain in contrast to the gradual build-up of velocity gain. Notice also that gaze velocity remains substantially above zero (∼8°/s) for a long period (until head acceleration decreases).B: simulation of these data by the model, as described inInstantaneous VOR gain. In the model simulation, gaze velocity remained high throughout because head acceleration remained constant.
- Fig. 9.
A: VOR velocity gain as a function of time for distant targets, shown separately for 3 visibility conditions and darkness. Pooled values for 3 subjects and 2 directions. The VOR in darkness behaved similar to the way it did with a distant target; it made no difference whether the target was continuously visible or was extinguished shortly before head movement. Gain did not quite reach the “ideal” value. B: similar graphs for near visual targets; gain rose to higher values than it did for distant targets. Once again, the results were similar for continuously visible and interrupted targets. C: gain profiles compared for near and far targets (pooled data of 4 subjects).
- Fig. 10.
VOR velocity gain as a function of time for distant and near targets. Results for 4 subjects are shown separately inA–D but values for all available conditions of the visual target have been pooled.
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