Abstract
Does varying the start location of the left hand affect reaches to the felt (proprioceptive) or felt and seen (visual-proprioceptive) left hand? A robot manipulandum guided the left hand (actively) from one of 6 (start) sites to one of 5 remaining (target) sites. Participants reached with their right hand to the current felt or felt and seen (visible for 1 sec) location of the left hand or to remembered visual targets.
Participants were fairly accurate and precise when localizing the left hand, although less so than for visual targets (Mean horizontal error = 0.88cm, SD = 0.87cm; mean sagittal error = 1.24cm, SD = 0.96cm). Accuracy and precision of reach endpoints varied with target type. In the proprioceptive task, horizontal errors were deviated to the right. In both proprioceptive tasks sagittal errors were deviated towards the body, suggesting that participants felt their left hand to be closer to their body than its actual position. Proprioceptive reaches were also less precise (ellipse area = 3.96cm2) than visual-proprioceptive reaches (ellipse area = 1.39cm2) and visual reaches (ellipse area = 1.75cm2). There was no difference in precision for reaches to visual and visual-proprioceptive targets. These changes in accuracy and precision across target type do not vary with starting position of the left hand-target. We are currently assessing whether visual and proprioceptive information are optimally integrated within this task, and if integration varies with movement path of the hand-target.
