| Records |
| Author |
Portnoy, S.; Rosenberg, L.; Alazraki, T.; Elyakim, E.; Friedman, J. |
| 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 |
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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1050-6411 |
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77 |
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| Author |
Friedman, Jason; Brown, Scott; Finkbeiner, Matthew |
| Title |
Linking cognitive and reaching trajectories via intermittent movement control |
Type |
Journal Article |
| Year |
2013 |
Publication |
Journal of Mathematical Psychology |
Abbreviated Journal |
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| 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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70 |
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| Author |
Friedman, Jason; Flash, Tamar |
| Title |
Trajectory of the index finger during grasping |
Type |
Journal Article |
| Year |
2009 |
Publication |
Experimental Brain Research |
Abbreviated Journal |
Exp Brain Res |
| Volume |
196 |
Issue |
4 |
Pages |
497-509 |
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| Abstract |
The trajectory of the index finger during grasping movements was compared to the trajectories predicted by three optimization-based models. The three models consisted of minimizing the integral of the weighted squared joint derivatives along the path (inertia-like cost), minimizing torque change, and minimizing angular jerk. Of the three models, it was observed that the path of the fingertip and the joint trajectories, were best described by the minimum angular jerk model. This model, which does not take into account the dynamics of the finger, performed equally well when the inertia of the finger was altered by adding a 20 g weight to the medial phalange. Thus, for the finger, it appears that trajectories are planned based primarily on kinematic considerations at a joint level. |
| Address |
Department of Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel, write.to.jason@gmail.com |
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English |
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| ISSN |
1432-1106 |
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PMID:19521692 |
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no |
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Penn State @ write.to.jason @ |
Serial |
17 |
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| Author |
Noy, L.; Alon, U.; Friedman, J. |
| Title |
Corrective jitter motion shows similar individual frequencies for the arm and the finger |
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Journal Article |
| Year |
2015 |
Publication |
Experimental Brain Research |
Abbreviated Journal |
Exp Brain Res |
| Volume |
233 |
Issue |
4 |
Pages |
1307-1320 |
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| Abstract |
A characteristic of visuomotor tracking of non-regular oscillating stimuli are high-frequency jittery corrective motions, oscillating around the tracked stimuli. However, the properties of these corrective jitter responses are not well understood. For example, does the jitter response show an idiosyncratic signature? What is the relationship between stimuli properties and jitter properties? Is the jitter response similar across effectors with different inertial properties? To answer these questions, we measured participants' jitter frequencies in two tracking tasks in the arm and the finger. Thirty participants tracked the same set of eleven non-regular oscillating stimuli, vertically moving on a screen, once with forward-backward arm movements (holding a tablet stylus) and once with upward-downward index finger movements (with a motion tracker attached). Participants' jitter frequencies and tracking errors varied systematically as a function of stimuli frequency and amplitude. Additionally, there were clear individual differences in average jitter frequencies between participants, ranging from 0.7 to 1.15 Hz, similar to values reported previously. A comparison of individual jitter frequencies in the two tasks showed a strong correlation between participants' jitter frequencies in the finger and the arm, despite the very different inertial properties of the two effectors. This result suggests that the corrective jitter response stems from common neural processes. |
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0014-4819 |
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PMID:25630905 |
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76 |
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| Author |
Zopf, Regine; Truong, Sandra; Finkbeiner, Matthew; Friedman, Jason; Williams, Mark A |
| Title |
Viewing and feeling touch modulates hand position for reaching |
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Journal Article |
| Year |
2011 |
Publication |
Neuropsychologia |
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49 |
Issue |
5 |
Pages |
1287–1293 |
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| Abstract |
Action requires knowledge of our body location in space. Here we asked if interactions with the external world prior to a reaching action influence how visual location information is used. We investigated if the temporal synchrony between viewing and feeling touch modulates the integration of visual and proprioceptive body location information for action. We manipulated the synchrony between viewing and feeling touch in the Rubber Hand Illusion paradigm prior to participants performing a ballistic reaching task to a visually specified target. When synchronous touch was given, reaching trajectories were significantly shifted compared to asynchronous touch. The direction of this shift suggests that touch influences the encoding of hand position for action. On the basis of this data and previous findings, we propose that the brain uses correlated cues from passive touch and vision to update its own position for action and experience of self-location. |
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Penn State @ write.to.jason @ |
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23 |
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