Eye–hand coordination
From Wikipedia, the free encyclopedia
eye–hand coordination (or hand–eye coordination) is the coordinated control of eye movement with hand movement, and the processing of visual input to guide reaching and grasping. It has been studied in activities as diverse as tea making, the movement of solid objects such as wooden blocks, sporting performance, music reading, online first person computer gaming, and copy-typing. It is a way of performing everyday tasks and in its absence most people would be unable to carry out even the simplest of actions such as picking up a book from a table or playing a video game.
Contents |
[edit] Behavior and kinematics
Neuroscientists have investigated both the temporal and spatial aspects of eye–hand coordination. Sometimes the eyes appear to be locked onto the goal for a hand movement until it is reached. At other times the eyes appear to scout ahead toward other objects of interest before the hand grasps and manipulates the object. Conversely, humans are also able to aim eye movements toward the hand without vision, using the sense of proprioception, with only minor errors related to the internal knowledge of limb position.
The eyes and hand are also coordinated in the sense that plans for reaching or pointing to visual objects appear to be updated each time the eyes move, such that targets are remembered relative to the pointing directions of the eyes (gaze direction). This is known as gaze-centered remapping and also occurs for remembered targets for rapid eye movements called saccades. Humans are also able to take eye position into account when aiming a reach or pointing movement toward a remembered target.
[edit] Neural mechanisms
The neural control of eye–hand coordination is complex because it involves every part of the central nervous system involved in vision, eye movements, touch, and hand control. This includes the eyes themselves, the cerebral cortex, subcortical structures (such as the cerebellum, basal ganglia, and brainstem), the spinal cord, and the peripheral nervous system. Some of the areas involved in eye–hand coordination that have been most studied most intensely are the frontal and parietal cortex areas for saccade and reach control. The area of cortex around the intraparietal cortex, leading up to the parietal-occipital junction, has subdivisions for reach, grasp, and saccades. However, when single neurons are recorded in these areas, the reach areas often show some saccade-related responses and the saccade areas often show some reach related responses. This may aid in eye–hand coordination.
Many of these areas, in addition to controlling saccades or reach, also show eye position signals that are required for transforming visual signals into motor commands. In addition, some of the areas involved in reach, like the medial intraparietal cortex, show a gaze-centred remapping of responses during eye movements in both monkeys and humans.
[edit] Clinical syndromes
Optic ataxia is a clinical problem associated with parietal damage that affects eye–hand coordination. Optic ataxia patients usually have troubles reaching toward visual objects on the side of the world opposite to the side of brain damage. Often these problems are relative to current gaze direction, and appear to be remapped along with changes in gaze direction. Some patients with damage to the parietal cortex show 'magnetic reaching': a problem in which reaches seem drawn toward the direction of gaze, even when it is deviated from the desired object of grasp.
[edit] References
Johansson RS, Westling G, Bäckström A, Flanagan JR (2001) Eye–hand co-ordination in object manipulation, Journal of Neuroscience, 21(17), 6917–32
Crawford JD, Medendorp WP, Marotta JJ. Spatial transformations for eye–hand coordination. (2004) Journal of Neurophysiology,92(1),10-19 (Review)
