Interference from distractors in reach-to-grasp movements

Descriptions of interference effects from non-relevant stimuli are extensiv e in visual target detection and identification paradigms. To explore the i nfluence of features of non-relevant objects on reach-to-grasp movements, w e instructed healthy normal controls to reach for and pick up a cylinder (t arget) placed midsagittally 30 cm from the starting position of the hand. I n Experiment 1, the target was presented alone, or accompanied by a narrowe r, wider, or same-size distracter positioned to the left or right of the ta rget. In Experiment 2, the target was presented alone or accompanied by a d istractor, which was slanted at a different orientation to the target. Refl ective markers were placed on the wrist, thumb, and index finger of the rig ht hand, and infra-red light-detecting cameras recorded their displacement through a calibrated 3-dimensional working space. Kinematic parameters were derived and analysed. Consistent changes in the expression of peak velocit y, acceleration, and deceleration were evident when the distracter was narr ower or wider than the target. The impact of the orientation of the distrac tor, conversely, was not marked. We discuss the results in the context of p hysiological findings and models of selective attention.