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| Author | Kapur, Shweta; Friedman, Jason; Zatsiorsky, Vladimir M.; Latash, Mark L. | ||||
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Finger interaction in a three-dimensional pressing task | Type | Journal Article | ||
| Year | 2010 | Publication | Experimental Brain Research | Abbreviated Journal | |
| Volume | 203 | Issue | 1 | Pages | 101-118 |
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| Abstract | Accurate control of forces produced by the fingers is essential for performing object manipulation. This study examines the indices of finger interaction when accurate time profiles of force are produced in different directions, while using one of the fingers or all four fingers of the hand. We hypothesized that patterns of unintended force production among shear force components may involve features not observed in the earlier studies of vertical force production. In particular, we expected to see unintended forces generated by non-task fingers not in the direction on the instructed force but in the opposite direction as well as substantial force production in directions orthogonal to the instructed direction. We also tested a hypothesis that multi-finger synergies, quantified using the framework of the uncontrolled manifold hypothesis, will help reduce across-trials variance of both total force magnitude and direction. Young, healthy subjects were required to produce accurate ramps of force in five different directions by pressing on force sensors with the fingers of the right (dominant) hand. The index finger induced the smallest unintended forces in non-task fingers. The little finger showed the smallest unintended forces when it was a non-task finger. Task fingers showed substantial force production in directions orthogonal to the intended force direction. During four-finger tasks, individual force vectors typically pointed off the task direction, with these deviations nearly perfectly matched to produce a resultant force in the task direction. Multi-finger synergy indices reflected strong co-variation in the space of finger modes (commands to fingers) that reduced variability of the total force magnitude and direction across trials. The synergy indices increased in magnitude over the first 30% of the trial time and then stayed at a nearly constant level. The synergy index for stabilization of total force magnitude was higher for shear force components as compared to the downward pressing force component. The results suggest complex interactions between enslaving and synergic force adjustments, possibly reflecting the experience with everyday prehensile tasks. For the first time, the data document multi-finger synergies stabilizing both shear force magnitude and force vector direction. These synergies may play a major role in stabilizing the hand action during object manipulation. |
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| Notes | in press | Approved | no | ||
| Call Number | Penn State @ write.to.jason @ | Serial | 20 | ||
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| Author | Portnoy, S.; Mimouni-Bloch, A.; Rosenberg, L.; Offek, H.; Berman, T.; Kochavi, M.; Orman, G.; Friedman, J. | ||||
| Title |
Graphical Product Quality and Muscle Activity in Children With Mild Disabilities Drawing on a Horizontally or Vertically Oriented Tablet | Type | Journal Article | ||
| Year | 2018 | Publication | American Journal of Occupational Therapy | Abbreviated Journal | Am J Occup Ther |
| Volume | 72 | Issue | 6 | Pages | 1-7 |
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| Abstract | OBJECTIVE. We compared performance level and muscle activity patterns during shape copying and tracing in two positions, while sitting at a desk and while standing in front of a wall, between typically developing (TD) preschool children and children with mild disabilities (MD). METHOD. Twenty-two TD children (8 boys, 14 girls; mean [M] age 5 5.2 yr, standard deviation [SD] 5 0.1) and 13 children with MD (9 boys, 4 girls; M age 5 4.9 yr, SD 5 0.5) participated in this study. RESULTS. The children performed faster and smoother movements when copying shapes on the vertical surface, with no reduction of accuracy, than on the horizontal surface. Children with MD exerted their upper trapezius while performing the short tasks on the vertical surface compared with their muscle activity on the horizontal surface. CONCLUSION. Incorporating short copying or drawing tasks on a vertical surface may increase the control of proximal muscles and ease graphomotor performance in children with MD. |
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| ISSN | 0272-9490 | ISBN | Medium | ||
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| Notes | Approved | no | |||
| Call Number | Penn State @ write.to.jason @ | Serial | 91 | ||
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| Author | Kaufman-Cohen, Y.; Levanon, Y.; Friedman, J.; Yaniv, Y.; Portnoy, S. | ||||
| Title |
Home exercise in the dart-throwing motion plane after distal radius fractures: A Pilot Randomized Controlled Trial | Type | Journal Article | ||
| Year | 2020 | Publication | Journal of Hand Therapy | Abbreviated Journal | |
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| Notes | Approved | no | |||
| Call Number | Serial | 103 | |||
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| Author | Liebermann, D.G.; Biess, A.; Friedman, J.; Gielen, C.C.A.M.; Flash, T. | ||||
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Intrinsic joint kinematic planning. I: reassessing the Listing's law constraint in the control of three-dimensional arm movements | Type | Journal Article | ||
| Year | 2006 | Publication | Experimental Brain Research | Abbreviated Journal | Exp Brain Res |
| Volume | 171 | Issue | 2 | Pages | 139-154 |
| Keywords | Adolescent; Adult; Analysis of Variance; *Arm; Biomechanics; Eye Movements/*physiology; Humans; Joints/*physiology; Male; Movement/*physiology; *Musculoskeletal System; Orientation/*physiology; Posture | ||||
| Abstract | This study tested the validity of the assumption that intrinsic kinematic constraints, such as Listing's law, can account for the geometric features of three-dimensional arm movements. In principle, if the arm joints follow a Listing's constraint, the hand paths may be predicted. Four individuals performed 'extended arm', 'radial', 'frontal plane', and 'random mixed' movements to visual targets to test Listing's law assumption. Three-dimensional rotation vectors of the upper arm and forearm were calculated from three-dimensional marker data. Data fitting techniques were used to test Donders' and Listing's laws. The coefficient values obtained from fitting rotation vectors to the surfaces described by a second-order equation were analyzed. The results showed that the coefficients that represent curvature and twist of the surfaces were often not significantly different from zero, particularly not during randomly mixed and extended arm movements. These coefficients for forearm rotations were larger compared to those for the upper arm segment rotations. The mean thickness of the rotation surfaces ranged between approximately 1.7 degrees and 4.7 degrees for the rotation vectors of the upper arm segment and approximately 2.6 degrees and 7.5 degrees for those of the forearm. During frontal plane movements, forearm rotations showed large twist scores while upper arm segment rotations showed large curvatures, although the thickness of the surfaces remained low. The curvatures, but not the thicknesses of the surfaces, were larger for large versus small amplitude radial movements. In conclusion, when examining the surfaces obtained for the different movement types, the rotation vectors may lie within manifolds that are anywhere between curved or twisted manifolds. However, a two-dimensional thick surface may roughly represent a global arm constraint. Our findings suggest that Listing's law is implemented for some types of arm movement, such as pointing to targets with the extended arm and during radial reaching movements. | ||||
| Address | Department of Physical Therapy, Sackler Faculty of Medicine, Tel-Aviv University, 69978, Ramat Aviv, Israel. dlieberm@post.tau.ac.il | ||||
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| Language | English | Summary Language | Original Title | ||
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| ISSN | 0014-4819 | ISBN | Medium | ||
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| Notes | PMID:16341526 | Approved | no | ||
| Call Number | Penn State @ write.to.jason @ | Serial | 18 | ||
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| Author | Friedman, J.; Korman, M. | ||||
| Title |
Kinematic Strategies Underlying Improvement in the Acquisition of a Sequential Finger Task with Self-Generated vs. Cued Repetition Training | Type | Journal Article | ||
| Year | 2012 | Publication | PLoS one | Abbreviated Journal | PLoS One |
| Volume | 7 | Issue | 12 | Pages | e52063 |
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| Abstract | Many motor skills, such as typing, consist of articulating simple movements into novel sequences that are executed faster and smoother with practice. Dynamics of re-organization of these movement sequences with multi-session training and its dependence on the amount of self-regulation of pace during training is not yet fully understood. In this study, participants practiced a sequence of key presses. Training sessions consisted of either externally (Cued) or self-initiated (Uncued) training. Long-term improvements in performance speed were mainly due to reducing gaps between finger movements in both groups, but Uncued training induced higher gains. The underlying kinematic strategies producing these changes and the representation of the trained sequence differed significantly across subjects, although net gains in speed were similar. The differences in long-term memory due to the type of training and the variation in strategies between subjects, suggest that the different neural mechanisms may subserve the improvements observed in overall performance. | ||||
| Address | Department of Cognitive Science, Macquarie University, Sydney, Australia ; ARC Centre of Excellence in Cognition and its Disorders, Macquarie University, Sydney, Australia | ||||
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| ISSN | 1932-6203 | ISBN | Medium | ||
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| Notes | PMID:23272210 | Approved | no | ||
| Call Number | Serial | 41 | |||
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