hide
Free keywords:
-
Abstract:
Vestibulo-ocular reex (VOR) responses of humans to whole body rotations are well known.
Along with other parameters, the VOR-gain (eye velocity / head velocity) may be used to
evaluate the functional status of the VOR. Although VOR gain is known to show great individual
variability, we sought to determine whether the adaptive plasticity of VOR gain may
give insight about individual strategies for optimal spatial orientation. The question of whether
the oculomotor responses would be different between a group of experts (gym - high performance
gymnasts), with a high degree of spatial abilities, and a control group of non-athletes
(control), was of particular interest. The subjects' (gym: n = 9, age: 1012 years, control: n
= 10, age: 1012 years) eye movements were recorded using a video nystagmography system
(SMI). They were seated with head xed in a software controlled multiaxial whole body rotator.
The test consisted of a combination of a two simultaneous sinusoidal 360
rotations about
the pitch and yaw axes, followed by the reverse motion, simulating movements of twisting
somersaults. The maximum velocity was 113 deg/s in each axis, and duration was 10 sec for
the whole test (0.1 Hz). Each subject was rst rotated without knowledge of the nature of the
stimulus, followed by a repetition where the subjects knew the same test would occur. This was
compared to a standard sinusoidal monoaxial (horizontal) test (0.1 Hz, 100 deg/s). Although
correctly directed eye movements were observed during all phases of the whole body rotation
(including in a companion study with double twists), initial comparisons were performed
on the horizontal components of eye movements and whole body rotation. The results show
no signicant difference between the gymnasts and controls for the sinusoidal test (gain
s.d.,gym.:0.48
0.06, n=9, non.:0.45
0.14, n=9; p=.565, Z=-.575, Mann-Whitney-U), and the
rst (w/o prior knowledge) multiaxial stimulus (gym.:0.48
0.05, n=8; non.:0.47
0.07, n=9;
p=.596, Z=-.531, Mann-Whitney-U). For the second (prior knowledge) multiaxial stimulus, the
difference was signicant ((gym.:0.39
0.05, n=6; non.:0.45
0.06, n=6; p=.037, Z=-2.085,
Mann-Whitney-U). Finding no difference for the tests without expectations of the stimulus
show that the reexive response has not been adapted in this context. But the signicant difference
following preparation of the stimulus shows the gymnasts suppress even reexive eye
movements. This is consistent with the companion poster indicating that gymnasts may rely
heavily on visual orientation mechanisms at the expense of vestibular responses, both cognitive
and oculomotor.
