Human Motion Perception and Visual Vestibular Integration

DOF Motion Platform

Our sense of vertical, heading direction, and our motion perception are importation for ambulation, navigation, and spatial orientation. Head motion is sensed by the vestibular end organs in the inner ear, however perception is also influenced by visual cues, optic flow, auditory cues, proprioception, and motor efferent copy. During natural activities these cues are almost always congruent and hence redundant information is available to the central nervous system.

This research project uses a hexapod motion platform which can deliver complex motion stimuli in all six degrees of freedom such as that achieved during ambulation. Other sensory stimuli can also be controlled or eliminated so that vestibular perception can be studied independently and the role of other factors can be isolated.

Test subject riding the motion platform

Initial projects involve measuring the thresholds and accuracy of rotation, translation, and tilt perception in normal controls and subjects with vestibular loss. The thresholds of visual and auditory perception and how they are affected by aging and pathological states are well known and are part of standard clinical testing, however the limits and accuracy of vestibular perception are currently unknown. Establish these thresholds in normal controls and as well as subjects with known vestibular lesions, may be useful in developing more useful clinical testing of the vestibular system.

One key roll of the vestibular system is to maintain gaze stability during ambulation through the action of the vestibulo-ocular reflex or VOR. We know that vestibular function declines with age and that the way the head moves during ambulation also changes. Although most motor and sensory systems decline with age, oscillopsia or visual blurring with head motion is not a part of the normal aging process indicating the that VOR maintains its compensatory ability. One mechanism for compensation of vestibular loss is limitation of head motion as commonly observed in patients with acute labyrinthitis. It is not clear if the changes in head motion seen during ambulation are a result of aging or are compensatory for the loss of vestibular function or both. By independently controlling head motion by simulating the translation and rotation observed during different types of ambulation, we hope to define the role of head motion during vestibular compensation.

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