| Records |
| 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 |
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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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1432-1106 |
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PMID:19554319 |
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no |
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Penn State @ write.to.jason @ |
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16 |
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| Author |
Awasthi, Bhuvanesh; Friedman, Jason; Williams, Mark A |
| Title |
Processing of low spatial frequency faces at periphery in choice reaching tasks |
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Journal Article |
| Year |
2011 |
Publication |
Neuropsychologia |
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| Volume |
49 |
Issue |
7 |
Pages |
2136-2141 |
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| Abstract |
Various aspects of face processing have been associated with distinct ranges of spatial frequencies. Configural processing of faces depends chiefly on low spatial frequency (LSF) information whereas high spatial frequency (HSF) supports feature based processing. However, it has also been argued that face processing has a foveal-bias (HSF channels dominate the fovea). Here we used reach trajectories as a continuous behavioral measure to study perceptual processing of faces. Experimental stimuli were LSF–HSF hybrids of male and female faces superimposed and were presented peripherally and centrally. Subject reached out to touch a specified sex and their movements were recorded. The reaching trajectories reveal that there is less effect of (interference by) LSF faces at fovea as compared to periphery while reaching to HSF targets. These results demonstrate that peripherally presented LSF information, carried chiefly by magnocellular channels, enables efficient processing of faces, possibly via a retinotectal (subcortical) pathway. |
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24 |
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Steinhart, S.; Weiss, P.L.; Friedman, J. |
| Title |
Proximal and distal movement patterns during a graphomotor task in typically developing children and children with handwriting problems |
Type |
Journal Article |
| Year |
2021 |
Publication |
Journal of Neuroengineering and Rehabilitation |
Abbreviated Journal |
J Neuroeng Rehabil |
| Volume |
18 |
Issue |
1 |
Pages |
178 |
| Keywords |
Arm; Biomechanical Phenomena; Child; *Handwriting; Humans; Motor Skills; *Movement; Upper Extremity; Distal joints; Handwriting; Motor control; Movement analysis; Proximal; Stability |
| Abstract |
BACKGROUND: Therapists specializing in handwriting difficulties in children often address motor problems including both proximal and distal movements in the upper extremity. Kinematic measures can be used to investigate various aspects of handwriting. This study examined differences in movement patterns in proximal and distal joints of the upper extremity during graphomotor tasks between typically developing children with and without handwriting problems. Additionally, it explored relationships between movement patterns, speed, and legibility of writing. METHODS: Forty-one children, aged 7-11 years, were assessed with the Aleph Aleph Ktav Yad Hebrew Handwriting assessment and the Beery Test of Visual Motor Integration and, based on their scores, were divided into a research group (with handwriting difficulties) and a control group (without handwriting difficulties). Upper extremity joint movement patterns were analyzed with a motion capture system. Differences in the quality of shapes traced and copied on a graphics tablet positioned horizontally and vertically were compared. Between-group differences and relationships with speed and legibility were analyzed. RESULTS: In both groups, there was greater movement in the distal compared to the proximal joints, greater movement when performing the task in a horizontal compared to a vertical plane, and greater movement when tracing than copying. Joint movements in the arm executed scaled-down versions of the shapes being drawn. While the amount of joint displacement was similar between groups, children in the research group showed greater dissimilarity between the drawn shape and the shape produced by the proximal joints. Finally, the drawing measure on the tablet was a significant predictor of legibility, speed of writing, visual motor integration and motor coordination, whereas the dissimilarity measure of joint movement was a significant predictor of speed of writing and motor coordination. CONCLUSIONS: This study provides support for the role of the distal upper extremity joints in the writing process and some guidance to assist clinicians in devising treatment strategies for movement-related handwriting problems. While we observed differences in proximal joint movements between the children with and without handwriting difficulties, the extent to which they are responsible for the differences in drawing quality remains to be determined. Further studies should use a similar methodology to examine additional tasks such as drawing shapes of varying sizes. |
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Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel. jason@tau.ac.il |
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1743-0003 |
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PMID:34930334; PMCID:PMC8690895 |
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no |
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118 |
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| Author |
Awasthi, Bhuvanesh; Friedman, Jason; Williams, Mark A |
| Title |
Reach Trajectories Reveal Delayed Processing of Low Spatial Frequency Faces in Developmental Prosopagnosia |
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Journal Article |
| Year |
2012 |
Publication |
Cognitive Neuroscience |
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| Volume |
3 |
Issue |
2 |
Pages |
120-130 |
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Developmental prosopagnosia (DP) is characterized by a selective deficit in face recognition despite normal cognitive and neurological functioning. Previous research has established configural processing deficits in DP subjects. Low spatial frequency (LSF) information subserves configural face processing. Using hybrid stimuli, here we examined the evolution of perceptual dynamics and integration of LSF information by DP subjects while they pointed to high spatial frequency (HSF) face targets. Permutation analysis revealed a 230-ms delay in LSF processing by DP subjects as compared to controls. This delayed processing is likely to contribute to the difficulties associated with face recognition in DP subjects and is reflective of their alleged reliance on local rather than global features in face perception. These results suggest that quick and efficient processing of LSF information is critical for the development of normal face perception. |
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Penn State @ write.to.jason @ |
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27 |
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| Author |
Salzer, Y.; Friedman, J. |
| Title |
Reaching trajectories unravel modality-dependent temporal dynamics of the automatic process in the Simon task: a model-based approach |
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Journal Article |
| Year |
2020 |
Publication |
Psychological Research |
Abbreviated Journal |
Psychol Res |
| Volume |
84 |
Issue |
6 |
Pages |
1700-1713 |
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The Simon effect represents a phenomenon in which the location of the stimuli affects the speed and accuracy of the response, despite being irrelevant for the task demands. This is believed to be due to an automatic activation of a response corresponding to the location of the stimuli, which conflicts with the controlled decision process based on relevant stimuli features. Previously, differences in the nature of the Simon effect (i.e., the pattern of change of the effect across the distribution of response times) between visual and somatosensory stimuli were reported. We hypothesize that the temporal dynamics of visual and somatosensory automatic and controlled processes vary, thus driving the reported behavioral differences. While most studies have used response times to study the underlying mechanisms involved, in this study we had participants reach out to touch the targets and recorded their arm movements using a motion capture system. Importantly, the participants started their movements before a final decision was made. In this way, we could analyze the movements to gain insights into the competition between the automatic and controlled processes. We used this technique to describe the results in terms of a model assuming automatic activation due to location-based evidence, followed by inhibition. We found that for the somatosensory Simon effect, the decay of the automatic process is significantly slower than for the visual Simon effect, suggesting quantitative differences in this automatic process between the visual and somatosensory modalities. |
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0340-0727 |
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PMID:30980236 |
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97 |
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