The effects of intermittent vision on prehension under binocular and monocular viewing.

The aim of the present study was to examine the effects of intermittent binocular and monocular vision on the preparation and execution of the transport and grasp phases of prehension, and hence the temporal limit of binocular and monocular integration. Participants in two groups (speed or accuracy) performed prehensile movements of two amplitudes (20 and 40 cm) to either a large or small object (6 x 6 x 2 and 6 x 4x 2 cm) under conditions of binocular and monocular viewing. The interval between visual samples was manipulated with liquid crystal goggles (continuous vision, 20on/60off, and 20on/120off ms). A kinematic analysis indicated that participants modified variables associated with the preparation and execution of prehension in the intermittent vision conditions when instructed to emphasize accuracy. Participants instructed to emphasize speed, modified variables associated with the preparation phase only. The impact of intermittent vision was similar under binocular and monocular viewing. Thus, for prehension, it appears that consecutive binocular or monocular samples need to occur less than 60 ms apart in order to be fully integrated for limb control.