Abstract
Rotations of the line of sight are mainly implemented by coordinated motion of the eyes and head. Here, we propose a model for the kinematics of three-dimensional (3-D) head-unrestrained gaze-shifts. The model was designed to account for major principles in the known behavior, such as gaze accuracy, spatiotemporal coordination of saccades with vestibulo-ocular reflex (VOR), relative eye and head contributions, the non-commutativity of rotations, and Listing's and Fick constraints for the eyes and head, respectively. The internal design of the model was inspired by known and hypothesized elements of gaze control physiology. Inputs included retinocentric location of the visual target and internal representations of initial 3-D eye and head orientation, whereas outputs were 3-D displacements of eye relative to the head and head relative to shoulder. Internal transformations decomposed the 2-D gaze command into 3-D eye and head commands with the use of three coordinated circuits: (1) a saccade generator, (2) a head rotation generator, (3) a VOR predictor. Simulations illustrate that the model can implement: (1) the correct 3-D reference frame transformations to generate accurate gaze shifts (despite variability in other parameters), (2) the experimentally verified constraints on static eye and head orientations during fixation, and (3) the experimentally observed 3-D trajectories of eye and head motion during gaze-shifts. We then use this model to simulate how 2-D eye-head coordination strategies interact with 3-D constraints to influence 3-D orientations of the eye-in-space, and the implications of this for spatial vision.
Highlights
Gaze-shifts, i.e., rapid reorientations of the line of sight, are the primary motor mechanism for re-directing foveal vision and attention in humans and other primates (Bizzi et al, 1971; Tomlinson and Bahra, 1986a; Tomlinson, 1990; Guitton, 1992; Corneil and Munoz, 1996)
Failure to properly account for this, in our model, would result in saccade errors that increase with the position component and length of retinal error
We have assumed that these rules are perfectly implemented downstream from the output of our model so our model cannot predict any such “blips.” eye trajectories become much more complicated in the headunrestrained situation because saccades must be coordinated with the vestibulo-ocular reflex (VOR), which does not obey Listing’s law, resulting in large transient deviations of eye position from Listing’s plane (Crawford and Vilis, 1991; Tweed et al, 1998; Crawford et al, 1999; Klier et al, 2003)
Summary
Gaze-shifts, i.e., rapid reorientations of the line of sight, are the primary motor mechanism for re-directing foveal vision and attention in humans and other primates (Bizzi et al, 1971; Tomlinson and Bahra, 1986a; Tomlinson, 1990; Guitton, 1992; Corneil and Munoz, 1996). The final positions of gaze-shifts of various amplitudes and directions are simulated in Figure 5 for the eye-in-head (left column), head-inspace (middle column), and eye-in-space (right column), where the first row shows the 2-D components of this range and the second row shows horizontal position plotted as a function of torsional position.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
