The contribution of visual and proprioceptive information to the precision of reaching movements

Abstract

We examined how the precision of ballistic reaching movements was affected by the availability of visual and proprioceptive information. Twelve right-handed subjects made reaching movements with the index finger of their right hand either to an external target or to the fingertip of their left hand (body target), which had been passively moved to the target location by the experimenter. Subjects always had a 2-s preview of the target, followed by a delay of 2-s, after which the reaching was initiated under three different levels of vision: no vision, brief vision until the initiation of the movement, or full vision until the end of the movement. We measured the error of the final reaching position with respect to the target. The addition of proprioceptive information (body vs. external target) improved precision when vision was limited (no vision or brief vision) but not when full vision was available. Moreover, the addition of proprioceptive target information had different effects on errors in movement amplitude vs. heading (side-to-side direction). Movement amplitude errors were small when proprioceptive information was available, regardless of the amount of visual information. In contrast, heading errors depended on the amount of visual information available even when proprioceptive information was also provided. These results suggest that proprioception is particularly valuable in encoding the distance of the target (and the amplitude of the required reach), while vision is particularly valuable in encoding the direction of the target (and the heading of the reach).

Footnotes

 This research was funded by a grant from the Natural Sciences and Engineering Research Council of Canada to Jody C. Culham. The authors want to thank Haitao Yang for the technical assistance.