A Quantitative Analysis for Decomposing Visual Signal of the Gaze Displacement

When the head is unrestrained, the large amplitude gaze shifts are composed of coordinated eye and head movements. The position of the eyes at the onset of the gaze shift can alter the eye and head contributions to the movement. The movements of the eyes and head during the unrestrained-head gaze shift follow well-defined relationships. It is possible to predict the displacement of the eye and head components of the gaze shift, if the position of the target signal in the retina and the initial eye position in the orbit are known. In the present study we provide a quantitative analysis for decomposing the gaze displacement signal and propose a mathematical model to predict the displacement of the eye and head components of the gaze shift. We conclude that the displacements of the eye and the head components are determined by five factors: the current gaze displacement, the initial eye position, the upper limit of the range in which the eyes move freely without head contribution, the lower limit of the range in which the head moves only, and the maximal displacement of the visual target (maximal initial retinal error). The results of our proposed model are inline with data observed physiologically.