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Author Ezrati, O.; Friedman, J.; Dar, R. pdf  url
doi  openurl
  Title Attenuation of access to internal states in high obsessive-compulsive individuals might increase susceptibility to false feedback: Evidence from a visuo-motor hand-reaching task Type Journal Article
  Year 2019 Publication (up) Journal of Behavior Therapy and Experimental Psychiatry Abbreviated Journal Journal of Behavior Therapy and Experimental Psychiatry  
  Volume 65 Issue Pages 101445  
  Keywords Obsessive-compulsive disorder; Movement; Agency; Proprioception; Proxies  
  Abstract Background and objectives

The Seeking Proxies for Internal States (SPIS) model of obsessive-compulsive disorder (OCD) posits that obsessive-compulsive (OC) individuals have attenuated access to their internal states. Hence, they seek and rely on proxies, or discernible substitutes for these internal states. In previous studies, participants with high OC tendencies and OCD patients, compared to controls, showed increased reliance on external proxies and were more influenced by false feedback when judging their internal states. This study is the first to examine the effects of false feedback on performance of hand movements in participants with high and low OC tendencies.

Method

Thirty-four participants with high OC tendencies and 34 participants with low OC tendencies were asked to perform accurate hand reaches without visual feedback in two separate sessions of a computerized hand-reaching task: once after valid feedback training of their hand location and once with false-rotated feedback. We assessed the accuracy and directional adaptation of participants' reaches.

Results

As predicted, high OC participants evidenced a larger decrease in their hand positioning accuracy after training with false feedback compared to low OC participants.

Limitations

The generalization of our findings to OCD requires replication with a clinical sample.

Conclusions

These results suggest that in addition to self-perceptions, motor performance of OC individuals is prone to be overly influenced by false feedback, possibly due to attenuated access to proprioceptive cues. These findings may be particularly relevant to understanding the distorted sense of agency in OCD.
 
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  ISSN 0005-7916 ISBN Medium  
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  Notes Approved no  
  Call Number Serial 95  
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Author Portnoy, S.; Rosenberg, L.; Alazraki, T.; Elyakim, E.; Friedman, J. pdf  url
doi  openurl
  Title Differences in Muscle Activity Patterns and Graphical Product Quality in Children Copying and Tracing Activities on Horizontal or Vertical Surfaces Type Journal Article
  Year 2015 Publication (up) Journal of Electromyography and Kinesiology Abbreviated Journal Journal of Electromyography and Kinesiology  
  Volume 25 Issue 3 Pages 540�547  
  Keywords Motor equivalence; Electromyography; Tablet; Occupational Therapy; Muscle fatigue; Motor control  
  Abstract The observation that a given task, e.g. producing a signature, looks similar when created by different motor commands and different muscles groups is known as motor equivalence. Relatively little data exists regarding the characteristics of motor equivalence in children. In this study, we compared the level of performance when performing a tracing task and copying figures in two common postures: while sitting at a desk and while standing in front of a wall, among preschool children. In addition, we compared muscle activity patterns in both postures. Specifically, we compared the movements of 35 five- to six-year old children, recording the same movements of copying figures and path tracing on an electronic tablet in both a horizontal orientation, while sitting, and a vertical orientation, while standing. Different muscle activation patterns were observed between the postures, however no significant difference in the performance level was found, providing evidence of motor equivalence at this young age. The study presents a straightforward method of assessing motor equivalence that can be extended to other stages of development as well as motor disorders.  
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  ISSN 1050-6411 ISBN Medium  
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  Notes Approved no  
  Call Number Serial 77  
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Author Kaufman-Cohen, Y.; Levanon, Y.; Friedman, J.; Yaniv, Y.; Portnoy, S. pdf  openurl
  Title Home exercise in the dart-throwing motion plane after distal radius fractures: A Pilot Randomized Controlled Trial Type Journal Article
  Year 2020 Publication (up) Journal of Hand Therapy Abbreviated Journal  
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  Notes Approved no  
  Call Number Serial 103  
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Author Friedman, Jason; Brown, Scott; Finkbeiner, Matthew pdf  doi
openurl 
  Title Linking cognitive and reaching trajectories via intermittent movement control Type Journal Article
  Year 2013 Publication (up) Journal of Mathematical Psychology Abbreviated Journal  
  Volume 57 Issue 3-4 Pages 140-151  
  Keywords Decision making; Diffusion model; Reaction times; Arm movements; Submovements  
  Abstract Theories of decision-making have traditionally been constrained by reaction time data. A limitation of reaction time data, particularly for studying the temporal dynamics of cognitive processing, is that they index only the endpoint of the decision making process. Recently, physical reaching trajectories have been used as proxies for underlying mental trajectories through decision space. We suggest that this approach has been oversimplified: while it is possible for the motor control system to access the current state of the evidence accumulation process, this access is intermittent. Instead, we demonstrate how a model of arm movements that assumes intermittent, not continuous, access to the decision process is sufficient to describe the effects of stimulus quality and viewing time in curved reaching movements.  
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  Notes Approved no  
  Call Number Serial 70  
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Author Friedman, J; Latash, M.L.; Zatsiorsky, V.M. pdf  doi
openurl 
  Title Directional variability of the isometric force vector produced by the hand in multi-joint planar tasks Type Journal Article
  Year 2011 Publication (up) Journal of Motor Behavior Abbreviated Journal  
  Volume 43 Issue 6 Pages 451-463  
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  Abstract Numerous studies have examined control of force magnitude, but relatively little research has considered force direction control. In this study, subjects applied isometric forces to a handle and we compared within-trial variability when producing force in different directions. The standard deviation (SD) of the force parallel to the prescribed direction of force production increased linearly with the targeted force level, as did the SD of the force perpendicular to the instructed direction. In contrast, the SD of the angle of force production decreased with increased force level. In the four (of eight) instructed force directions where the endpoint force was generated due to a joint torque in only one joint (either the shoulder or elbow) the principal component axes in force space were well aligned with the prescribed direction of force production. In the other directions, the variance was approximately equal along the two force axes. The variance explained by the first principal component was significantly larger in torque space compared to the force space, and mostly corresponded to positive correlation between the joint torques. Such coordinated changes suggest that the torque variability was mainly due to the variability of the common drive to the muscles serving two joints, although this statement needs to be supported by direct studies of muscle activation in the future.  
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  Notes Approved no  
  Call Number Penn State @ write.to.jason @ Serial 26  
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