Visuomotor Control
These studies show how visual motion affects reaching movements: the manual following response.
2005
Visual motion due to eye movements helps guide the hand.
Movement of the body, head, or eyes with respect to the world creates one of the most common yet complex situations in which the visuomotor system must localize objects. In this situation, vestibular, proprioceptive, and extra-retinal information contribute to accurate visuomotor control. The utility of retinal motion information, on the other hand, is questionable, since a single pattern of retinal motion can be produced by any number of head or eye movements. Here we investigated whether retinal motion during a smooth pursuit eye movement contributes to visuomotor control. When subjects pursued a moving object with their eyes and reached to the remembered location of a separate stationary target, the presence of a moving background significantly altered the endpoints of their reaching movements. A background that moved with the pursuit, creating a retinally stationary image (no retinal slip), caused the endpoints of the reaching movements to deviate in the direction of pursuit, overshooting the target. A physically stationary background pattern, however, producing retinal image motion opposite to the direction of pursuit, caused reaching movements to become more accurate. The results indicate that background retinal motion is used by the visuomotor system in the control of visually guided action.
2003
The influence of visual motion on fast reaching movements to a stationary object.
One of the most important functions of vision is
to direct actions to objects. However, every time that vision is used
to guide an action, retinal motion signals are produced by the movement
of the eye and head as the person looks at the object or by the motion
of other objects in the scene. To reach for the object accurately, the
visuomotor system must separate information about the position of the
stationary target from background retinal motion signals—a
long-standing problem that is poorly understood. Here we show that the
visuomotor system does not distinguish between these two information
sources: when observers made fast reaching movements to a briefly
presented stationary target, their hand shifted in a direction
consistent with the motion of a distant and unrelated stimulus, a
result contrary to most other findings. This can be seen early in the
hand’s trajectory and occurs continuously from programming of the
movement through to its execution. The visuomotor system might make use
of the motion signals arising from eye and head movements to update the
positions of targets rapidly and redirect the hand to compensate for
body movements.
