Movement drift following visual occlusion of the hand and target B Cameron, J López-Moliner |
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Institute for Brain, Cognition and Behaviour, University of Barcelona, Spain
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| Without hand vision, reaches not only become more variable, but they also systematically drift away from their original target. This has sometimes been attributed to a deterioration of the proprioceptive estimate of the hand without recalibration by vision. Here we test the hypothesis that drift is due to optimal integration of misaligned sensory estimates, rather than any decay or shift in the proprioceptive estimate of the hand [Smeets et al, 2006, PNAS, 103(49), 18781-18786]. We examined movement drift over the course of 40 back-and-forth movements when (1) vision of the hand was occluded, (2) vision of the targets was occluded, and (3) vision of the hand and targets was occluded. On some trials, we introduced direct proprioceptive information about the targets (the non-dominant hand beneath the reaching surface) to increase the reliability of the proprioceptive estimate of the target. We observed equal drift magnitude in the no-target and no-hand vision conditions, and the most drift when neither hand nor target was visible. Presence of a proprioceptive target influenced the direction of drift, but did not influence the magnitude of drift. Our results are only partially consistent with Smeets et al’s model. |
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