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Kinematics and Plasticity of the Vestibulo-Ocular Reflex

The vestibular system, through the vestibulo-ocular reflex (VOR) maintains vision during angular (aVOR) and linear (lVOR) head movements by producing compensatory eye movements that stabilize images on the retina. The lVOR is kinematically demanding, requiring adjustment in the size stabilizing eye movements in response to a variety of geometric factors such as gaze angle and target distance. For example, the closer the target is being viewed, the larger the compensatory response that is required. I am studying how the vestibular system incorporates this information into the eye movement response, and the capabilities and nature of adaptive control of such influences.

Investigations on adaptive plasticity in the LVOR include a novel form of adaptation in which subjects view the world through prisms that shift the effective straight ahead during NO motion. We know from previous work that the NO-LVOR switches direction around this point, as is geometrically appropriate (a motor null-point, corresponding to the focus of expansion of visual optic flow). We have demonstrated that the reflex (in darkness) can shift this motor inversion point correctly after prism adaptation. Other paradigms address the plastic calibration of the vergence influence on the LVOR, using periscopic optics to alter the effective inter-ocular separation, and therefore the vergence required to fixate targets at all distances.