Abstract
Vision is obtained with a continuous motion of the eyes. The kinematic analysis of eye motion, during any visual or ocular task, typically reveals two (kinematic) components: saccades, which quickly replace the visual content in the retinal fovea, and drifts, which slowly scan the image after each saccade. While the saccadic exchange of regions of interest (ROIs) is commonly considered to be included in motor-sensory closed-loops, it is commonly assumed that drifts function in an open-loop manner, that is, independent of the concurrent visual input. Accordingly, visual perception is assumed to be based on a sequence of open-loop processes, each initiated by a saccade-triggered retinal snapshot. Here we directly challenged this assumption by testing the dependency of drift kinematics on concurrent visual inputs using real-time gaze-contingent-display. Our results demonstrate a dependency of the trajectory on the concurrent visual input, convergence of speed to condition-specific values and maintenance of selected drift-related motor-sensory controlled variables, all strongly indicative of drifts being included in a closed-loop brain-world process, and thus suggesting that vision is inherently a closed-loop process.
Highlights
The visual system usually perceives its environment during egomotion [1,2,3]
Our results suggest that this initial boost of drift speed is the beginning of a convergence process, a process through which the oculomotor system converges upon a target drift speed that fits the characteristics of the current condition
Our results provide substantial evidence that this acquisition is accomplished by retino-neuro-oculo closed-loops, involving low levels of the visual system
Summary
The visual system usually perceives its environment during egomotion [1,2,3]. In particular, retinal encoding results from continuous interactions between eye movements and the environment [1, 4,5,6,7,8,9,10]. The kinematics of eye movements contain two major motion components: saccades, which quickly (speeds between ~10 to ~1000 deg/s) shift the gaze from one region of interest (ROI) to another [11,12,13] and drifts, which slowly (speeds in the order of 1 deg/s) scan each ROI [1, 14,15,16]. These two kinematic components, saccades and drifts, fully characterize the movements during all kinds of visual activities, whether while fixating, pursuing moving targets, reading or exploring a scene. It is currently accepted that all saccades can be characterized along the same kinematic continuum, controlled by the same circuits, and serve the same
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