Anticipatory responses to perturbation of co-ordination in one-handed catching.

Anticipatory responses to perturbation have rarely been studied in the co-ordination of dynamic interceptive actions. In this study, the kinematics of ball catching were examined in skilled catchers when mechanical perturbation of the catching arm was expected and unexpected. During trials where the perturbation was anticipated, participants initiated movements earlier (207 +/- 32 ms) than in randomly perturbed trials (223 +/- 34 ms). Furthermore, several individuals also tended to move their hand faster when perturbations were expected compared to baseline trials. Individual analyses revealed that three out of eight participants exhibited changes in the relative timing of the grasp phase to adapt to the specific manipulation of task constraints. Anticipatory responses were revealed in changes not only at movement initiation but also in the resulting adaptations to the co-ordination of reach and grasp phases of ball catching. When the catchers could not anticipate perturbations, movement strategies suggested the use of a continuous tracking-based mode of control rather than a prediction-based mode of control.