A model is presented to predict human dynamic spatial orientation in response to multisensory stimuli. Motion stimuli are first processed by dynamic models of the visual, vestibular, tactile, and proprioceptive sensors. Central nervous system function is modeled as a steady state Kalman filter that optimally blends information from the various sensors to form an estimate of spatial orientation. Where necessary, nonlinear elements preprocess inputs to the linear central estimator in order to reflect more accurately some nonlinear human response characteristics. Computer implementation of the model has shown agreement with several important qualitative characteristics of human spatial orientation.

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The terms eye movement measurement, eye tracking, and oculogragphy refer to measurement of the orientation and motion of the eye, either with respect to the head, or with respect to the visual environment. This may include not only rotations of the eye that cause changes in gaze direction, but also rotations of the eyeball about the line of sight, called ocular torsion. Eye movement measurement devices have long been used for research in reading, various aspects of visual perception and cognition, neurology, human factors, and marketing. In recent years, practical uses have expanded to include as computer usability research, communication devices for the disabled, sports and gait research, Lasik surgery instrumentation, and research requiring simultaneous functional magnetic resonance imaging (f MRI) measurement. The eye movement measurement techniques currently in most frequent use fall into the major categories of magnetic search coil, a technique that measures magnetically induced current in a tiny wire coil fastened to the eye; electro oculography, which uses surface electrodes to measure the direction of an electrical potential between the cornea and retina; and optical techniques that rely on optical sensors to detect the position or motion of features on the eye. The optical technique category includes many subtypes, and has the largest variety of different systems in current use. Background theory and system descriptions are presented for eye movement measurement devices in all of the above categories.