The effects of delay on the kinematics of grasping.

摘要: We examined the effect on manual prehension of introducing a 5-s delay between viewing target object and initiating grasping movement. Subjects were tested in four conditions: three involved fourth estimating its size. In main experimental condition (Open Loop Delay), subjects viewed for 300 ms, but did not initiate movement until an auditory signal was presented 5 s later. this condition, had to rely stored visual information guiding their grasp after delay. another Loop), initiated as soon appeared. both these open-loop conditions, reached out grasped without seeing hand. third (Closed hand visible throughout reach. instructed pick up across width using index finger thumb. final (Perceptual Estimation), gave estimate object's with thumb ms. all which height, length independently varied from trial trial. The results experiment indicated that reaching movements made Open-Loop Closed-Loop conditions differ any kinematic measures. contrast, when performed Delay reaches took significantly longer achieved peak velocity proportionately earlier. As well, maximum grip aperture larger. addition, affected by (the 'relevant' dimension) height. estimates Perceptual-Estimation however, reflected only width. These results, together evidence other studies, suggest motor actions use different transformations than those used 'real-time' grasping. argue drive delayed arises perceptual rather visuomotor analysis object.