Abstract

TEIXEIRA, Luis  and  FRANZONI, Mariana. Time course of timing reprogramming in interception is modulated by uncertainty on velocity alteration. Rev. Port. Cien. Desp. [online]. 2005, vol.5, n.2, pp.167-173. ISSN 1645-0523.

Reprogramming of interceptive actions is required when an abrupt unexpected modification in target velocity takes place. In such a situation, the original timing specifications have to be replaced by other ones appropriate for the new characteristics of the target motion in a short period of time. In this study, we contrasted two sources of uncertainty on target velocity modification in an interceptive task, probability and direction of change, and analyzed the time course of movement timing reprogramming. Participants tried to synchronize the action of hitting a hemiball with the arrival of a moving target at the end of an electronic trackway. The target was initially displaced at a constant velocity of 3 m/s, and in some trials its velocity was unexpectedly changed to 2 m/s or 4 m/s at different moments before interception. Participants were assigned to one of two groups: 25% or 50% probability of target velocity alteration, with both groups facing conditions of uni and bidirectional velocity change. The results showed a gradual increment of temporal accuracy as a function of longer times after velocity change, revealing the continuous nature of timing reprogramming. The lowest uncertainty condition led to the best movement reprogramming, producing more accurate timing responses throughout situations of changed velocity.

Keywords : movement reprogramming; continuous models; moving targets; sensorimotor control.

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