Position coding in a video-controlled pointing task with a rotated visual display: evidence for individual differences in visuo-proprioceptive interaction

In video-controlled tasks, visuomotor performance is generally initially poor with rotated visual display, but improves through trial-by-trial learning. We hypothesise that the inaccurate processing of the visual hand-to-target vector mainly results from the persistent influence of non-visual information relating to arm posture. To test this hypothesis, arm-related proprioceptive and visual information were independently manipulated in a video-controlled pointing task. Analysis of movement vectors revealed that the target was located according to the visual hand but its proprioceptive orientation (Allelocentric(1) system of reference, N = 10), or according to the proprioceptive hand location and orientation (Egocentric system of reference, N = 8). The prevalence of one system of reference correlated with the accuracy of proprioceptive signals informing about arm posture. One obstacle in mastering video-controlled task results thus from the persistent influence of proprioceptive information in the spatial coding of visual goals for action, which however differs across individuals. (C) 2004 Elsevier Ireland Ltd. All rights reserved.