Bs. Mesland et al., OBJECT MOTION PERCEPTION DURING EGO-MOTION - PATIENTS WITH A COMPLETELOSS OF VESTIBULAR FUNCTION VS NORMALS, Brain research bulletin, 40(5-6), 1996, pp. 459-465
Object motion perception was assessed in avestibular patients and norm
al controls. Two experiments were conducted, in which subjects were re
quired to assess the motion of a visual stimulus with respect to earth
. In the first experiment, we measured the velocity at which a briefly
presented (200 ms) grating was perceived as earth fixed, while the su
bject maintained fixation on a visual target fixed relative to the bod
y, during whole-body yaw rotation (VOR suppression). In this experimen
tal setup, the influence of the semicircular canal signals on object m
otion perception was evaluated. The avestibular patients judged the gr
ating to be stationary with respect to earth, when it was moving at th
e same velocity as their body, whereas for normal controls, the gratin
g was perceived as stationary when it moved at a velocity slower than
their body motion, but greater than zero. The difference between the t
wo subject groups was significant, and showed the strong contribution
of the vestibular system to object motion perception. Similarly, a mea
surement of the velocity at which a grating was perceived as stationar
y was obtained during smooth pursuit eye movements. In this experiment
the contribution of the efference copy of the oculomotor signal and p
roprioceptive signals to object motion perception were assessed. As wi
th the first experiment, the normal controls displayed a more veridica
l sense of object motion perception than the patients, although the di
fference was only just significant. We suggest that the difference cou
ld be an adaptive change in the patients perception of motion, which a
llows them to reduce the effects of oscillopsia.