Abstract
It has been suggested that the precise metrics of grasping movements directed to visible objects are computed in real-time and are therefore unaffected by previous experience or any earlier programming (Cant, et al., 2005, Neuropsychologia, 43(2), 216–226). We have tested whether the properties of a visually presented distractor object can influence the kinematics of a subsequent grasping movement performed under full vision. Ten participants grasped a target object after viewing a small or large elliptical distractor object in a certain orientation (0° or 30°). The target object appeared at the same location and could be either the same object in the same orientation as the distractor, or a circular object, which is neutral in orientation. When grasping the circular target object, grip orientation was affected in the direction of the previously presented distractor object. That is, at the time of maximum grip aperture grip orientation was 23.3° ± 2.2° after having seen the distractor in 0° orientation and 28.9° ± 1.6° after having seen the distractor in 30° orientation. Moreover, as in classical visuomotor priming, grasping movements were initiated 30ms ± 4ms faster when distractor and target were identical. Our study provides evidence that the planning of fully visually guided movements is influenced by prior perceptual experience. This planning is reflected in a change of movement parameters, in particular grip orientation, by the properties of the previously perceived object. This finding challenges the notion that grasping movements are controlled on the basis of real-time information alone.
This research is supported by DFG-Grant FR 2100/1-2