The vestibulo-ocular reflex (VOR) stabilizes the gaze during rapid head movements by inducing an eye rotation of equivalent amplitude but in the opposite direction to the head rotation. Normally, the ratio of eye rotation amplitude to head rotation, or VOR gain, is 1. Under some conditions such as growth or the use of corrective glasses, this gain is adapted to the new visuo-vestibular conditions. This well-known sensorimotor adaptation phenomenon can be achieved through the experimental creation of a conflict between vestibular and visual information. Incremental velocity error (IVE) allows for a rapid adaption of the VOR at high speed by synchronously projecting a laser target that moves to create a progressively increasing visuo-vestibular conflict. However, this method does not correspond to the ecological conditions of VOR use, as the training is conducted in darkness and the visuo-vestibular conflict does not involve the entire visual scene. Recreating this type of adaptation in a virtual reality environment could allow for adaptation with a visual stimulus involving the entire visual scene, thus more closely resembling the physiological conditions of VOR use. We hypothesize that a visual simulation of the entire scene would be more effective than an isolated target in VOR adaptation during high velocity head rotation.
Study Type
OBSERVATIONAL
Enrollment
18
Subjects will undergo adaptation of their VOR in virtual reality in two different conditions. The side on which the adaptation will take place and the type of condition with which the patients will start will be randomized. Subject will undergo passive rapid head movements done by an experienced examinator whilst fixing a target in front of them. The movement of the target relative to the movement of the head will increase every 90 seconds by 10% until the movement of the visual scene is twice that of the head movement. In one condition the visual scene will be only a target in a grey void. In the other condition the visual scene will be more complex and represent a target in the room in which the subject is seated. Subjects will undergo both conditions at least 7 days apart.
Hôpital Neurologique
Bron, France
VOR gain
VOR gain corresponds to the amplitude of the eye rotation devided by the amplitude of the head rotation for a given head impulse.
Time frame: 7 days
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