![]() Hand position matching experiments, in which the participant indicates the location of an occluded hand by matching its location with the other hand, show that without vision, the accuracy with which finger location is reported declines over repeated matches such that perception of limb position appears to drift ( Paillard and Brouchon 1968 Wann and Ibrahim 1993 Wolpert et al. Perception of limb position with respect to both the body and the external world depends on information provided by vision, proprioception, and touch ( Graziano 1999 van Beers et al. These results suggest that proprioception continues to be a reliable source of limb position information after prolonged time without vision, but that this information is used differently for maintaining limb position and for specifying movement trajectory. Inverse dynamics analysis revealed that movement preservation was accompanied by substantial modification of joint muscle torque. However, despite these dramatic changes in hand position and joint configuration, movement distance and direction remained relatively constant. This drift varied systematically with movement direction, indicating that drift is related to movement production. Over the 70 trials, the start location of each movement drifted, on average, 8 cm away from the initial start location. Movements were made in two directions (30° and 120°) from each of three start locations (initial shoulder angles of 30°, 40°, 50°, and initial elbow angles of 90°). Feedback was then removed, and participants were to continue on pace for the next 70 trials. Fingertip position feedback was given by a cursor during the first five trials in the series. To test this hypothesis, we asked participants to perform six series of 75 repetitive movements from a visible start location to a visible target, in time with a regular, audible tone. If this account is correct, drift should degrade the accuracy of movement distance and direction over a series of movements made without visual feedback. Such drift has been attributed to a gradual reduction in the usefulness of proprioception to signal limb position. ![]() To learn more, go to the absence of visual feedback, subject reports of hand location tend to drift over time. This release contains many improvements, such as better performance of the reactive viscoelastic framework, faster startup of FSI models, box constraints for constrained levmar optimization, new rendering features, and more. ![]() ![]() FEBio Studio 1.8 has been released! It comes with FEBio 3.7.The FEBio software downloads and knowledgebase can be found here. This will allow you to stay up to date on recent activity on the forum. You can subscribe to forums by pressing the "Subscribe" button at the top of the forum. Moderators are here to assist with explaining novel features, addressing bug reports and reviewing feature requests, but the effectiveness of the forum depends critically on the participation of experienced users who can assist novices or share ideas and models that explore challenging problems. A broad level of participation is encouraged, to create a vibrant community that helps improve the quality and usefulness of these open-source/free software products. Forum participants are encouraged to post questions, as well as answer posts from others. This forum serves the community of FEBio and FEBio Studio users and developers. ![]()
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