| Records |
| Author |
Zopf, R.; Friedman, J.; Williams, M.A. |
| Title |
The plausibility of visual information for hand ownership modulates multisensory synchrony perception |
Type |
Journal Article |
| Year |
2015 |
Publication |
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Abbreviated Journal |
Experimental Brain Research |
| Volume |
233 |
Issue |
8 |
Pages |
2311-2321 |
| Keywords |
Multisensory perception; Temporal synchrony perception; Virtual hand; Body representations; Body ownership; Sensory predictions |
Abstract  |
We are frequently changing the position of our bodies and body parts within complex environments. How does the brain keep track of one’s own body? Current models of body ownership state that visual body ownership cues such as viewed object form and orientation are combined with multisensory information to correctly identify one’s own body, estimate its current location and evoke an experience of body ownership. Within this framework, it may be possible that the brain relies on a separate perceptual analysis of body ownership cues (e.g. form, orientation, multisensory synchrony). Alternatively, these cues may interact in earlier stages of perceptual processing—visually derived body form and orientation cues may, for example, directly modulate temporal synchrony perception. The aim of the present study was to distinguish between these two alternatives. We employed a virtual hand set-up and psychophysical methods. In a two-interval force-choice task, participants were asked to detect temporal delays between executed index finger movements and observed movements. We found that body-specifying cues interact in perceptual processing. Specifically, we show that plausible visual information (both form and orientation) for one’s own body led to significantly better detection performance for small multisensory asynchronies compared to implausible visual information. We suggest that this perceptual modulation when visual information plausible for one’s own body is present is a consequence of body-specific sensory predictions. |
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| Publisher |
Springer Berlin Heidelberg |
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| Language |
English |
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| ISSN |
0014-4819 |
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no |
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Serial |
78 |
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| Author |
Friedman, Jason; Latash, Mark L.; Zatsiorsky, Vladimir M. |
| Title |
Prehension synergies: a study of digit force adjustments to the continuously varied load force exerted on a partially constrained hand-held object |
Type |
Journal Article |
| Year |
2009 |
Publication |
Experimental Brain Research |
Abbreviated Journal |
Exp Brain Res |
| Volume |
197 |
Issue |
1 |
Pages |
1-13 |
| Keywords |
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| Abstract |
We examined how the digit forces adjust when a load force acting on a hand-held object continuously varies. The subjects were required to hold the handle still while a linearly increasing and then decreasing force was applied to the handle. The handle was constrained, such that it could only move up and down, and rotate about a horizontal axis. In addition, the moment arm of the thumb tangential force was 1.5 times the moment arm of the virtual finger (VF, an imagined finger with the mechanical action equal to that of the four fingers) force. Unlike the situation when there are equal moment arms, the experimental setup forced the subjects to choose between (a) sharing equally the increase in load force between the thumb and VF but generating a moment of tangential force, which had to be compensated by negatively co-varying the moment due to normal forces, or (b) sharing unequally the load force increase between the thumb and VF but preventing generation of a moment of tangential forces. We found that different subjects tended to use one of these two strategies. These findings suggest that the selection by the CNS of prehension synergies at the VF-thumb level with respect to the moment of force is non-obligatory and reflects individual subject preferences. This unequal sharing of the load by the tangential forces, in contrast to the previously observed equal sharing, suggests that the invariant feature of prehension may be a correlated increase in tangential forces rather than an equal increase. |
| Address |
Department of Kinesiology, The Pennsylvania State University, 39 Recreation Building, University Park, PA, 16802, USA, jason.friedman@psu.edu |
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English |
Summary Language |
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Series Issue |
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Edition |
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| ISSN |
1432-1106 |
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| Notes |
PMID:19554319 |
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no |
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Penn State @ write.to.jason @ |
Serial |
16 |
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| Author |
Raveh, E.; Portnoy, S.; Friedman, J. |
| Title |
Adding vibrotactile feedback to a myoelectric-controlled hand improves performance when online visual feedback is disturbed |
Type |
Journal Article |
| Year |
2018 |
Publication |
Human Movement Science |
Abbreviated Journal |
Hum Mov Sci |
| Volume |
58 |
Issue |
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Pages |
32-40 |
| Keywords |
Myoelectric prostheses; Sensorimotor control; Upper limb amputation; Visual feedback |
| Abstract |
We investigated whether adding vibrotactile feedback to a myoelectric-controlled hand, when visual feedback is disturbed, can improve performance during a functional test. For this purpose, able-bodied subjects, activating a myoelectric-controlled hand attached to their right hand performed the modified Box & Blocks test, grasping and manipulating wooden blocks over a partition. This was performed in 3 conditions, using a repeated-measures design: in full light, in a dark room where visual feedback was disturbed and no auditory feedback – one time with the addition of tactile feedback provided during object grasping and manipulation, and one time without any tactile feedback. The average time needed to transfer one block was measured, and an infrared camera was used to give information on the number of grasping errors during performance of the test. Our results show that when vibrotactile feedback was provided, performance time was reduced significantly, compared with when no vibrotactile feedback was available. Furthermore, the accuracy of grasping and manipulation was improved, reflected by significantly fewer errors during test performance. In conclusion, adding vibrotactile feedback to a myoelectric-controlled hand has positive effects on functional performance when visual feedback is disturbed. This may have applications to current myoelectric-controlled hands, as adding tactile feedback may help prosthesis users to improve their functional ability during daily life activities in different environments, particularly when limited visual feedback is available or desirable. |
| Address |
Physical Therapy Department, Sackler Faculty of Medicine, Tel Aviv University, Israel. Electronic address: jason@post.tau.ac.il |
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English |
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Series Issue |
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Edition |
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| ISSN |
0167-9457 |
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Conference |
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| Notes |
PMID:29353091 |
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no |
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Serial |
88 |
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| Author |
Biess, A.; Flash, T.; Liebermann, D.G. |
| Title |
Riemannian geometric approach to human arm dynamics, movement optimization, and invariance |
Type |
Journal Article |
| Year |
2011 |
Publication |
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics |
Abbreviated Journal |
Phys Rev E Stat Nonlin Soft Matter Phys |
| Volume |
83 |
Issue |
3 Pt 1 |
Pages |
031927 |
| Keywords |
Arm/*physiology; Biomechanics; Computer Simulation; Humans; Kinetics; Male; Models, Biological; Models, Statistical; Models, Theoretical; *Movement; Psychomotor Performance/*physiology; Range of Motion, Articular/physiology; Reaction Time/physiology; Space Perception/*physiology; Torque |
| Abstract |
We present a generally covariant formulation of human arm dynamics and optimization principles in Riemannian configuration space. We extend the one-parameter family of mean-squared-derivative (MSD) cost functionals from Euclidean to Riemannian space, and we show that they are mathematically identical to the corresponding dynamic costs when formulated in a Riemannian space equipped with the kinetic energy metric. In particular, we derive the equivalence of the minimum-jerk and minimum-torque change models in this metric space. Solutions of the one-parameter family of MSD variational problems in Riemannian space are given by (reparameterized) geodesic paths, which correspond to movements with least muscular effort. Finally, movement invariants are derived from symmetries of the Riemannian manifold. We argue that the geometrical structure imposed on the arm's configuration space may provide insights into the emerging properties of the movements generated by the motor system. |
| Address |
Bernstein Center for Computational Neuroscience, DE-37073 Gottingen, Germany. armin@nld.ds.mpg.de |
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English |
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Edition |
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| ISSN |
1539-3755 |
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| Notes |
PMID:21517543 |
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no |
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Serial |
29 |
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| Author |
Friedman, J.; Korman, M. |
| Title |
Observation of an expert model induces a skilled movement coordination pattern in a single session of intermittent practice |
Type |
Journal Article |
| Year |
2019 |
Publication |
Scientific Reports |
Abbreviated Journal |
Sci Rep |
| Volume |
9 |
Issue |
1 |
Pages |
4609 |
| Keywords |
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| Abstract |
We tested how observation of a skilled pattern of planar movements can assist in the learning of a new motor skill, which otherwise requires rigorous long-term practice to achieve fast and smooth performance. Sixty participants performed a sequence of planar hand movements on pre-test, acquisition, post-test and 24 h post-training blocks, under 1 of 4 conditions: an observation group (OG), a slowed observation group (SOG), a random motion control group (RMCG) and a double physical training control group (DPTCG). The OG and SOG observed an expert model's right hand performing the study task intermittently throughout acquisition, RMCG observed random dots movement instead of a model. Participants in the DPTCG received extra physical practice trials instead of the visually observed trials. Kinematic analysis revealed that only in conditions with observation of an expert model there was an instant robust improvement in motor planning of the task. This step-wise improvement was not only persistent in post-training retests but was also apparently implicit and subject to further incremental improvements in movement strategy over the period of 24 hours. The rapid change in motor strategy was accompanied by a transient within-session increase in spatial error for the observation groups, but this went away by 24 h post-training. We suggest that observation of hand movements of an expert model coaligned with self-produced movements during training can significantly condense the time-course of ecologically relevant drawing/writing skill mastery. |
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English |
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Edition |
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2045-2322 |
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| Notes |
PMID:30872661 |
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no |
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Serial |
94 |
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