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Author Dempsey-Jones, H.; Wesselink, D.B.; Friedman, J.; Makin, T.R. pdf  url
doi  openurl
  Title Organized Toe Maps in Extreme Foot Users Type Journal Article
  Year 2019 Publication (up) Cell Reports Abbreviated Journal Cell Reports  
  Volume 28 Issue 11 Pages 2748-2756.e4  
  Keywords  
  Abstract Although the fine-grained features of topographic maps in the somatosensory cortex can be shaped by everyday experience, it is unknown whether behavior can support the expression of somatotopic maps where they do not typically occur. Unlike the fingers, represented in all primates, individuated toe maps have only been found in non-human primates. Using 1-mm resolution fMRI, we identify organized toe maps in two individuals born without either upper limb who use their feet to substitute missing hand function and even support their profession as foot artists. We demonstrate that the ordering and structure of the artists’ toe representation mimics typical hand representation. We further reveal “hand-like” features of activity patterns, not only in the foot area but also similarly in the missing hand area. We suggest humans may have an innate capacity for forming additional topographic maps that can be expressed with appropriate experience.  
  Address  
  Corporate Author Thesis  
  Publisher Elsevier Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 2211-1247 ISBN Medium  
  Area Expedition Conference  
  Notes doi: 10.1016/j.celrep.2019.08.027 Approved no  
  Call Number Serial 99  
Permanent link to this record
 

 
Author Park, J.; Pazin, N.; Friedman, J.; Zatsiorsky, V.M.; Latash, M.L. pdf  url
doi  openurl
  Title Mechanical properties of the human hand digits: Age-related differences Type Journal Article
  Year 2014 Publication (up) Clinical Biomechanics Abbreviated Journal  
  Volume 29 Issue 2 Pages 129–137  
  Keywords hand; aging; friction; apparent stiffness; damping  
  Abstract Background

Mechanical properties of human digits may have significant implications for the hand function. We quantified several mechanical characteristics of individual digits in young and older adults.

Methods

Digit tip friction was measured at several normal force values using a method of induced relative motion between the digit tip and the object surface. A modified quick-release paradigm was used to estimate digit apparent stiffness, damping, and inertial parameters. The subjects grasped a vertical handle instrumented with force/moment sensors using a prismatic grasp with four digits; the handle was fixed to the table. Unexpectedly, one of the sensors yielded leading to a quick displacement of the corresponding digit. A second-order, linear model was used to fit the force/displacement data.

Findings

Friction of the digit pads was significantly lower in older adults. The apparent stiffness coefficient values were higher while the damping coefficients were lower in older adults leading to lower damping ratio. The damping ratio was above unity for most data in young adults and below unity for older adults. Quick release of a digit led to force changes in other digits of the hand, likely due to inertial hand properties. These phenomena of “mechanical enslaving” were smaller in older adults although no significant difference was found in the inertial parameter in the two groups.

Interpretations

The decreased friction and damping ratio present challenges for the control of everyday prehensile tasks. They may lead to excessive digit forces and low stability of the grasped object.
 
  Address  
  Corporate Author Thesis  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0268-0033 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 73  
Permanent link to this record
 

 
Author Raveh, E.; Friedman, J.; Portnoy, S. pdf  url
doi  openurl
  Title Evaluation of the effects of adding vibrotactile feedback to myoelectric prosthesis users on performance and visual attention in a dual-task paradigm Type Journal Article
  Year 2018 Publication (up) Clinical Rehabilitation Abbreviated Journal Clin Rehabil  
  Volume 99 Issue 11 Pages 2263-2270  
  Keywords  
  Abstract Objective: To evaluate the effects of adding vibrotactile feedback to myoelectric prosthesis users on the performance time and visual attention in a dual-task paradigm.

Design: A repeated-measures design with a counterbalanced order of two conditions.

Setting: Laboratory setting.

Subjects: Transradial amputees using a myoelectric prosthesis with normal or corrected eyesight (N=12, median age=65 ± 13 years). Exclusion criteria were orthopedic or neurologic problems.

Interventions: Subjects performed grasping tasks with their prosthesis, while controlling a virtual car on a road with their intact hand. The dual task was performed twice: with and without vibrotactile feedback.

Main measures: Performance time of each of the grasping tasks and gaze behavior, measured by the number of times the subjects shifted their gaze toward their hand, the relative time they applied their attention to the screen, and percentage of error in the secondary task.

Results: The mean performance time was significantly shorter (P=0.024) when using vibrotactile feedback (93.2 ± 9.6 seconds) compared with the performance time measured when vibrotactile feedback was not available (107.8 ± 20.3seconds). No significant differences were found between the two conditions in the number of times the gaze shifted from the screen to the hand, in the time the subjects applied their attention to the screen, and in the time the virtual car was off-road, as a percentage of the total game time

(51.4 ± 15.7 and 50.2 ± 19.5, respectively).

Conclusion: Adding vibrotactile feedback improved performance time during grasping in a dual-task paradigm. Prosthesis users may use vibrotactile feedback to perform better during daily tasks, when multiple cognitive demands are present.
 
  Address  
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  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0269-2155 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Penn State @ write.to.jason @ Serial 89  
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Author Liebermann, D.G.; Biess, A.; Friedman, J.; Gielen, C.C.A.M.; Flash, T. pdf  url
doi  openurl
  Title 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 (up) 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  
  Corporate Author Thesis  
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  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0014-4819 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:16341526 Approved no  
  Call Number Penn State @ write.to.jason @ Serial 18  
Permanent link to this record
 

 
Author Latash, M.L., Friedman, J., Kim, S.W., Feldman, A.G., Zatsiorsky, V.M. pdf  url
openurl 
  Title Prehension Synergies and Control with Referent Hand Configurations Type Journal Article
  Year 2010 Publication (up) Experimental Brain Research Abbreviated Journal Exp Brain Res  
  Volume 202 Issue 1 Pages 213-229  
  Keywords  
  Abstract We used the framework of the equilibrium-point hypothesis (in its updated form based on the notion of referent configuration) to investigate the multi-digit synergies at two levels of a hypothetical hierarchy involved in prehensile actions. Synergies were analyzed at the thumb-virtual finger level (virtual finger is an imaginary digit with the mechanical action equivalent to that of the four actual fingers) and at the individual finger level. The subjects performed very quick vertical movements of a handle into a target. A load could be attached off-center to provide a pronation or supination torque. In a few trials, the handle was unexpectedly fixed to the table and the digits slipped off the sensors. In such trials, the hand stopped at a higher vertical position and rotated into pronation or supination depending on the expected torque. The aperture showed non-monotonic changes with a large, fast decrease and further increase, ending up with a smaller distance between the thumb and the fingers as compared to unperturbed trials. Multi-digit synergies were quantified using indices of co-variation between digit forces and moments of force across unperturbed trials. Prior to the lifting action, high synergy indices were observed at the individual finger level while modest indices were observed at the thumb-virtual finger level. During the lifting action, the synergies at the individual finger level disappeared while the synergy indices became higher at the thumb-virtual finger level. The results support the basic premise that, within a given task, setting a referent configuration may be described with a few referent values of variables that influence the equilibrium state, to which the system is attracted. Moreover, the referent configuration hypothesis can help interpret the data related to the trade-off between synergies at different hierarchical levels.  
  Address  
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  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Penn State @ write.to.jason @ Serial 19  
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