Use of visual information in the correction of interceptive actions.

Use of visual information in interceptive actions requiring large-scale changes to movement timing was investigated. The task consisted of intercepting a moving target on a monitor screen through an angular arm movement. In half of the trials, the initial target velocity of 8 cm/s was unexpectedly decreased to 4 cm/s or increased to 12 cm/s, leaving 800 ms to target arrival after velocity change. Visual information about target displacement was manipulated by interpolating full vision with occlusion of the last 200, 400, or 600 ms before the due time of interception. The results revealed that reduction of visual exposure of target displacement affected movement variability, but not arm velocity or directional trend of temporal errors. This finding supports the concept that motor control in interception is based on an internal representation of target displacement, formed during the initial portion of visual exposure following velocity change, which is updated by further visual information of target displacement.