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Article

Development of Gaze Control in Early Infancy  

Kerstin Rosander

Gaze control involves eyes, head, and body movements and is guided by mainly three types of information: visual, vestibular, and proprioceptive. Appropriate gaze control is a basis for actions such as reaching, grasping, eating, and manipulation, all of which develop during the first year of life. The development of gaze control is about how young infants gain access to these different kinds of information, how they come to use them, and how they come to coordinate head and eyes to accomplish it. This control develops during the first few weeks of life. A major challenge for the gaze controlling system is how gaze is stabilized on a moving target to keep vision clear, including during self-motion or the compensation of other sudden movements. Furthermore, the tracking has to be timed relative to the object motion. This requires prediction, which is a part of smooth pursuit that emerges at around six weeks and is in full function at three months. The smooth eye and head movements must add up in time and space to the object motion. Then the vestibular and visual neural signals must be properly added. Catch-up saccades compensate when the smooth pursuit is insufficient. In other situations, saccades shift the gaze between objects or situations. Moreover, if a moving object temporarily disappears out of view, one or several saccades predictively recapture the object at the reappearance position (four months). The complex and fast development of gaze has inspired the design of robotic vision (iCub) through processes similar to human development, thus increasing the robot’s flexibility and learning abilities

Article

Eye Movements and Perception  

Doris I. Braun and Alexander C. Schütz

Voluntary eye movements and visual perception are closely intertwined in humans and nonhuman primates because of the limitation of high-acuity vision to a very small, specialized area at the center of the retina, the fovea. Only when the image of an object is projected on the foveal region by eye and head movements it is possible, to perceive fine visual details such as letters during reading. In order to improve visual perception and to benefit from high-resolution foveal vision, rapid saccadic eye movements frequently change the direction of both eyes to selected peripheral locations. Continuous sequences of these voluntary saccades and fixations determine what humans see and in how much detail they perceive objects and their visual surroundings. Where, when, and how humans move their eyes depends not only on the visual properties of the target object but also on their intentions and prevailing tasks. Accordingly, target locations for saccades differ depending on the things people do—whether they just look around, actively search for something, read, or do sports. Instead of the classical dichotomy of bottom-up and top-down processes, recent research on gaze behavior has focused on the dynamic interplay of factors such as task demands, rewards, scene content, temporal sequences, and individual and historical differences. Besides saccadic eye movements, humans are also able to rotate their eyes continuously when they pursue moving objects of interest. Smooth pursuit eye movements stabilize the image of a moving object on the foveal region and prevent degradation of the retinal target image resulting from motion smear. The use of pursuit eye movements also improves the prediction of future target movement. Pursuit initiation is often combined with interceptive saccades that direct the fovea to the moving target, and catch-up saccades that correct for small mismatches concerning eye and target position, speed, and/or direction. Because each eye movement alters retinal input, compensations for retinal displacements are needed to maintain a stable representation of the environment. Overall, both saccadic and smooth pursuit eye movements provide optimal uptake of visual information for perception and guidance of actions.