The Experts below are selected from a list of 6183 Experts worldwide ranked by ideXlab platform
Mark L Latash - One of the best experts on this subject based on the ideXlab platform.
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Prehension synergies and hand function in early-stage Parkinson's disease.
Experimental brain research, 2014Co-Authors: Jaebum Park, Mechelle M. Lewis, Xuemei Huang, Mark L LatashAbstract:We explored the multi-digit synergies and hand performance in object manipulations and pressing tasks in patients with early-stage Parkinson’s disease (PD) and healthy controls. Synergies were defined as inter-trials co-variation patterns among forces/moments produced by individual digits that stabilized a resultant mechanical variable. The subjects performed three main tasks: pressing (steady-state force production followed by a force pulse into the target), Prehension (manipulation of a handheld instrumented handle imitating the action of taking a sip from a glass), and functional object manipulation (moving a glass with water as quickly and accurately as possible along a chain of targets). The PD patients were slower compared to controls in all three tasks. Patients showed smaller synergy indices in the pressing and Prehension tasks. In the Prehension tasks, patients showed elevated grip force at steady states with smaller grip force modulation during the handle motion. PD patients showed smaller feed-forward synergy adjustments in preparation to the quick action in the pressing and (to a smaller degree) Prehension tasks. Synergy indices correlated with the time index of performance in the functional glass-with-water task, whereas none of the indices correlated with the Unified PD Rating Scale part III—motor scores. We interpret the results as pointing at an important role of subcortical structures in motor synergies and their feed-forward adjustments to action.
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Stability of the multi-finger Prehension synergy studied with transcranial magnetic stimulation.
Experimental brain research, 2008Co-Authors: Xun Niu, Vladimir M Zatsiorsky, Mark L LatashAbstract:We used transcranial magnetic stimulation (TMS) to explore the stability of the three constituents of the multi-finger Prehension synergy. Patterns of co-variation between mechanical variables produced by individual digits were used as indices of the Prehension synergy. We tested hypotheses that TMS would violate these patterns and that different components of the Prehension synergy would take different times to restore. Subjects held an instrumented handle with one of the three external load and one of the seven external torques statically in the air. Single-pulse TMS was applied unexpectedly over the hand projection in the contralateral hemisphere. The normal forces showed a quick TMS-induced increase that was proportional to the background force magnitude. This was also true for the tangential forces produced by the thumb, middle, and ring fingers but not by the index and little fingers. The total moment of force changed proportionally to its background value with predominance of supination responses. During the quick force response to TMS, patterns of digit force co-variation stabilizing the total tangential force and total moment of force were violated. Two stages of synergy restoration were identified taking approximately 0.3 and 1.5 s. These times differed among the three synergy components. The results support the idea of a Prehension synergy as a neural mechanism that facilitates conjoint changes in forces produced by individual digits with the purpose to stabilize the hand action on the hand-held object. The data also support applicability of the principle of superposition to the human hand action.
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Multifinger Prehension: an overview.
Journal of motor behavior, 2008Co-Authors: Vladimir M Zatsiorsky, Mark L LatashAbstract:The authors review the available experimental evidence on what people do when they grasp an object with several digits and then manipulate it. The article includes three parts, each addressing a specific aspect of multifinger Prehension. In the first part, the authors discuss manipulation forces (i.e., the resultant force and moment of force exerted on the object) and the digits' contribution to such forces' production. The second part deals with internal forces defined as forces that cancel each other and do not disturb object equilibrium. The authors discuss the role of the internal forces in maintaining the object stability, with respect to such issues as slip prevention, tilt prevention, and resistance to perturbations. The third part is devoted to the motor control of Prehension. It covers such topics as Prehension synergies, chain effects, the principle of superposition, interfinger connection matrices and reconstruction of neural commands, mechanical advantage of the fingers, and the simultaneous d...
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Prehension synergies trial to trial variability and principle of superposition during static Prehension in three dimensions
Journal of Neurophysiology, 2005Co-Authors: Jae Kun Shim, Mark L Latash, Vladimir M ZatsiorskyAbstract:We performed three-dimensional analysis of the conjoint changes of digit forces during Prehension (Prehension synergies) and tested applicability of the principle of superposition to three-dimensio...
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Prehension synergies: effects of object geometry and prescribed torques.
Experimental brain research, 2002Co-Authors: Vladimir M Zatsiorsky, Fan Gao, Mark L LatashAbstract:We studied the coordination of forces and moments exerted by individual digits in static tasks that required balancing an external load and torque. Subjects (n=10) stabilized a handle with an attachment that allowed for change of external torque. Thumb position and handle width systematically varied among the trials. Each subject performed 63 tasks (7 torque values × 3 thumb locations × 3 widths). Forces and moments exerted by the digit tips on the object were recorded. Although direction and magnitude of finger forces varied among subjects, each subject used a similar multidigit synergy: a single eigenvalue accounted for 95.2–98.5% of the total variance. When task parameters were varied, regular conjoint digital force changes (Prehension synergies) were observed. Synergies represent preferential solutions used by the subjects to satisfy mechanical requirements of the tasks. In particular, chain effects in force adjustments to changes in the handle geometry were documented. An increased handle width induced the following effects: (a) tangential forces remained unchanged, (b) the same tangential forces produced a larger moment Tt, (c) the increased Tt was compensated by a smaller moment of the normal forces Tn, and (d) normal finger forces were rearranged to generate a smaller moment. Torque control is a core component of Prehension synergies. Observed Prehension synergies are only mechanically necessitated in part. The data support a theory of hierarchical organization of Prehension synergies.
Vladimir M Zatsiorsky - One of the best experts on this subject based on the ideXlab platform.
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Stability of the multi-finger Prehension synergy studied with transcranial magnetic stimulation.
Experimental brain research, 2008Co-Authors: Xun Niu, Vladimir M Zatsiorsky, Mark L LatashAbstract:We used transcranial magnetic stimulation (TMS) to explore the stability of the three constituents of the multi-finger Prehension synergy. Patterns of co-variation between mechanical variables produced by individual digits were used as indices of the Prehension synergy. We tested hypotheses that TMS would violate these patterns and that different components of the Prehension synergy would take different times to restore. Subjects held an instrumented handle with one of the three external load and one of the seven external torques statically in the air. Single-pulse TMS was applied unexpectedly over the hand projection in the contralateral hemisphere. The normal forces showed a quick TMS-induced increase that was proportional to the background force magnitude. This was also true for the tangential forces produced by the thumb, middle, and ring fingers but not by the index and little fingers. The total moment of force changed proportionally to its background value with predominance of supination responses. During the quick force response to TMS, patterns of digit force co-variation stabilizing the total tangential force and total moment of force were violated. Two stages of synergy restoration were identified taking approximately 0.3 and 1.5 s. These times differed among the three synergy components. The results support the idea of a Prehension synergy as a neural mechanism that facilitates conjoint changes in forces produced by individual digits with the purpose to stabilize the hand action on the hand-held object. The data also support applicability of the principle of superposition to the human hand action.
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Multifinger Prehension: an overview.
Journal of motor behavior, 2008Co-Authors: Vladimir M Zatsiorsky, Mark L LatashAbstract:The authors review the available experimental evidence on what people do when they grasp an object with several digits and then manipulate it. The article includes three parts, each addressing a specific aspect of multifinger Prehension. In the first part, the authors discuss manipulation forces (i.e., the resultant force and moment of force exerted on the object) and the digits' contribution to such forces' production. The second part deals with internal forces defined as forces that cancel each other and do not disturb object equilibrium. The authors discuss the role of the internal forces in maintaining the object stability, with respect to such issues as slip prevention, tilt prevention, and resistance to perturbations. The third part is devoted to the motor control of Prehension. It covers such topics as Prehension synergies, chain effects, the principle of superposition, interfinger connection matrices and reconstruction of neural commands, mechanical advantage of the fingers, and the simultaneous d...
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Prehension synergies trial to trial variability and principle of superposition during static Prehension in three dimensions
Journal of Neurophysiology, 2005Co-Authors: Jae Kun Shim, Mark L Latash, Vladimir M ZatsiorskyAbstract:We performed three-dimensional analysis of the conjoint changes of digit forces during Prehension (Prehension synergies) and tested applicability of the principle of superposition to three-dimensio...
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Prehension synergies: effects of object geometry and prescribed torques.
Experimental brain research, 2002Co-Authors: Vladimir M Zatsiorsky, Fan Gao, Mark L LatashAbstract:We studied the coordination of forces and moments exerted by individual digits in static tasks that required balancing an external load and torque. Subjects (n=10) stabilized a handle with an attachment that allowed for change of external torque. Thumb position and handle width systematically varied among the trials. Each subject performed 63 tasks (7 torque values × 3 thumb locations × 3 widths). Forces and moments exerted by the digit tips on the object were recorded. Although direction and magnitude of finger forces varied among subjects, each subject used a similar multidigit synergy: a single eigenvalue accounted for 95.2–98.5% of the total variance. When task parameters were varied, regular conjoint digital force changes (Prehension synergies) were observed. Synergies represent preferential solutions used by the subjects to satisfy mechanical requirements of the tasks. In particular, chain effects in force adjustments to changes in the handle geometry were documented. An increased handle width induced the following effects: (a) tangential forces remained unchanged, (b) the same tangential forces produced a larger moment Tt, (c) the increased Tt was compensated by a smaller moment of the normal forces Tn, and (d) normal finger forces were rearranged to generate a smaller moment. Torque control is a core component of Prehension synergies. Observed Prehension synergies are only mechanically necessitated in part. The data support a theory of hierarchical organization of Prehension synergies.
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EuroHaptics - Multi-finger Prehension Synergy: Exploration with Transcranial Magnetic Stimulation
Haptics: Perception Devices and Scenarios, 1Co-Authors: Mark L Latash, Xun Niu, Vladimir M ZatsiorskyAbstract:We used transcranial magnetic stimulation (TMS) to explore the stability of the three components of the multi-finger Prehension synergy during holding a vertically oriented object vertically in the air. TMS led to close to proportional changes in the mechanical variables produced by the digits. These changes violated synergy components that took different times to restore. Patterns of co-variation of the mechanical variables produced by individual digits corresponding to the equation of statics restored first followed by a change in the magnitude of the performance variables such as grip force, total tangential force, and total moment of force. The results support the principle of superposition as applied to the Prehension synergy.
Sukhvinder Kalsiryan - One of the best experts on this subject based on the ideXlab platform.
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changes in strength sensation and Prehension in acute cervical spinal cord injury european multicenter responsiveness study of the grassp
Neurorehabilitation and Neural Repair, 2015Co-Authors: Ingemarie Velstra, Sukhvinder Kalsiryan, Armin Curt, Angela Frotzler, Rainer Abel, Johan Swanik Rietman, Marc BolligerAbstract:Objective: To investigate the internal and external responsiveness and recovery profiles of the Graded Redefined Assessment of Strength, Sensibility, and Prehension (GRASSP) instrument in revealing changes in upper limb function within the first year following cervical spinal cord injury (SCI). Method: A European prospective, longitudinal, multicenter study assessing the GRASSP at 1, 3, 6, and 12 months after cervical SCI. Subtests of GRASSP were compared to the upper extremity motor (UEMS) and light touch scores (LT) according to the International Standards of Neurological Classification of Spinal Cord Injury (ISNCSCI), the Spinal Cord Independence Measure self-care subscore (SCIM-SS), as well as a clinician-rated outcome measure (CROM) of clinical relevance. Data were analyzed for GRASSP responsiveness and recovery rate over time. Results: Seventy-four participants entered the study. GRASSP subtests proved responsive (standardized response mean [SRM] ranged from 0.79 to 1.48 for strength, 0.50 to 1.03 for Prehension, and 0.14 to 0.64 for sensation) between all examination time points. In comparison, UEMS and LT showed lower responsiveness (SRM UEMS ranged from 0.69 to 1.29 and SRM LT ranged from 0.30 to −0.13). All GRASSP subtests revealed significant, moderate-to-excellent correlations with UEMS, LT, and SCIM-SS at each time point, and changes in GRASSP subtests were in accordance with the CROM. GRASSP Prehension and motor recovery was largest between 1 and 3 months. Conclusion: The GRASSP showed excellent responsiveness, detecting distinct changes in strength and Prehension relating to the severity of cervical SCI. It detected clinically significant changes complimentary to the ISNCSCI and SCIM-SS assessments.
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development of the graded redefined assessment of strength sensibility and Prehension grassp reviewing measurement specific to the upper limb in tetraplegia
Journal of Neurosurgery, 2012Co-Authors: Sukhvinder Kalsiryan, Armin Curt, Mary C Verrier, Michael G FehlingsAbstract:Object Primary outcome measures for the upper limb in trials concerning human spinal cord injury (SCI) need to distinguish between functional and neurological changes and require satisfying psychometric properties for clinical application. Methods The Graded Redefined Assessment of Strength, Sensibility and Prehension (GRASSP) was developed by the International GRASSP Research and Design Team as a clinical outcome measure specific to the upper limbs for individuals with complete and incomplete tetraplegia (that is, paralysis or paresis). It can be administered across the continuum of recovery after acute cervical SCI. An international multicenter study (involving centers in North America and Europe) was conducted to apply the measure internationally and examine its applicability. Results The GRASSP is a multimodal test comprising 5 subtests for each upper limb: dorsal sensation, palmar sensation (tested with Semmes-Weinstein monofilaments), strength (tested with motor grading of 10 muscles), and prehensio...
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assessment of the hand in tetraplegia using the graded redefined assessment of strength sensibility and Prehension grassp impairment versus function
Topics in Spinal Cord Injury Rehabilitation, 2009Co-Authors: Sukhvinder Kalsiryan, Armin Curt, Michael G Fehlings, Mary C VerrierAbstract:Objective: To refine the Graded and Redefined Assessment of Strength, Sensibility and Prehension (GRASSP) as a measure of upper limb impairment following cervical SCI. Method: A cross-sectional study assessed a cohort of neurologically stable patients with tetraplegia using a preliminary version of the GRASSP. Regression analysis was performed to determine the association between subcomponents of the GRASSP (impairment) and measures of function. The GRASSP was modified based on results. Results: Eliminated static two-point discrimination, tone, and one muscle. Conclusion: The GRASSP Version I consists of Semmes Weinstein monofilaments, manual muscle testing, and qualitative and quantitative Prehension testing.
Michael G Fehlings - One of the best experts on this subject based on the ideXlab platform.
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development of the graded redefined assessment of strength sensibility and Prehension grassp reviewing measurement specific to the upper limb in tetraplegia
Journal of Neurosurgery, 2012Co-Authors: Sukhvinder Kalsiryan, Armin Curt, Mary C Verrier, Michael G FehlingsAbstract:Object Primary outcome measures for the upper limb in trials concerning human spinal cord injury (SCI) need to distinguish between functional and neurological changes and require satisfying psychometric properties for clinical application. Methods The Graded Redefined Assessment of Strength, Sensibility and Prehension (GRASSP) was developed by the International GRASSP Research and Design Team as a clinical outcome measure specific to the upper limbs for individuals with complete and incomplete tetraplegia (that is, paralysis or paresis). It can be administered across the continuum of recovery after acute cervical SCI. An international multicenter study (involving centers in North America and Europe) was conducted to apply the measure internationally and examine its applicability. Results The GRASSP is a multimodal test comprising 5 subtests for each upper limb: dorsal sensation, palmar sensation (tested with Semmes-Weinstein monofilaments), strength (tested with motor grading of 10 muscles), and prehensio...
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assessment of the hand in tetraplegia using the graded redefined assessment of strength sensibility and Prehension grassp impairment versus function
Topics in Spinal Cord Injury Rehabilitation, 2009Co-Authors: Sukhvinder Kalsiryan, Armin Curt, Michael G Fehlings, Mary C VerrierAbstract:Objective: To refine the Graded and Redefined Assessment of Strength, Sensibility and Prehension (GRASSP) as a measure of upper limb impairment following cervical SCI. Method: A cross-sectional study assessed a cohort of neurologically stable patients with tetraplegia using a preliminary version of the GRASSP. Regression analysis was performed to determine the association between subcomponents of the GRASSP (impairment) and measures of function. The GRASSP was modified based on results. Results: Eliminated static two-point discrimination, tone, and one muscle. Conclusion: The GRASSP Version I consists of Semmes Weinstein monofilaments, manual muscle testing, and qualitative and quantitative Prehension testing.
Armin Curt - One of the best experts on this subject based on the ideXlab platform.
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changes in strength sensation and Prehension in acute cervical spinal cord injury european multicenter responsiveness study of the grassp
Neurorehabilitation and Neural Repair, 2015Co-Authors: Ingemarie Velstra, Sukhvinder Kalsiryan, Armin Curt, Angela Frotzler, Rainer Abel, Johan Swanik Rietman, Marc BolligerAbstract:Objective: To investigate the internal and external responsiveness and recovery profiles of the Graded Redefined Assessment of Strength, Sensibility, and Prehension (GRASSP) instrument in revealing changes in upper limb function within the first year following cervical spinal cord injury (SCI). Method: A European prospective, longitudinal, multicenter study assessing the GRASSP at 1, 3, 6, and 12 months after cervical SCI. Subtests of GRASSP were compared to the upper extremity motor (UEMS) and light touch scores (LT) according to the International Standards of Neurological Classification of Spinal Cord Injury (ISNCSCI), the Spinal Cord Independence Measure self-care subscore (SCIM-SS), as well as a clinician-rated outcome measure (CROM) of clinical relevance. Data were analyzed for GRASSP responsiveness and recovery rate over time. Results: Seventy-four participants entered the study. GRASSP subtests proved responsive (standardized response mean [SRM] ranged from 0.79 to 1.48 for strength, 0.50 to 1.03 for Prehension, and 0.14 to 0.64 for sensation) between all examination time points. In comparison, UEMS and LT showed lower responsiveness (SRM UEMS ranged from 0.69 to 1.29 and SRM LT ranged from 0.30 to −0.13). All GRASSP subtests revealed significant, moderate-to-excellent correlations with UEMS, LT, and SCIM-SS at each time point, and changes in GRASSP subtests were in accordance with the CROM. GRASSP Prehension and motor recovery was largest between 1 and 3 months. Conclusion: The GRASSP showed excellent responsiveness, detecting distinct changes in strength and Prehension relating to the severity of cervical SCI. It detected clinically significant changes complimentary to the ISNCSCI and SCIM-SS assessments.
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development of the graded redefined assessment of strength sensibility and Prehension grassp reviewing measurement specific to the upper limb in tetraplegia
Journal of Neurosurgery, 2012Co-Authors: Sukhvinder Kalsiryan, Armin Curt, Mary C Verrier, Michael G FehlingsAbstract:Object Primary outcome measures for the upper limb in trials concerning human spinal cord injury (SCI) need to distinguish between functional and neurological changes and require satisfying psychometric properties for clinical application. Methods The Graded Redefined Assessment of Strength, Sensibility and Prehension (GRASSP) was developed by the International GRASSP Research and Design Team as a clinical outcome measure specific to the upper limbs for individuals with complete and incomplete tetraplegia (that is, paralysis or paresis). It can be administered across the continuum of recovery after acute cervical SCI. An international multicenter study (involving centers in North America and Europe) was conducted to apply the measure internationally and examine its applicability. Results The GRASSP is a multimodal test comprising 5 subtests for each upper limb: dorsal sensation, palmar sensation (tested with Semmes-Weinstein monofilaments), strength (tested with motor grading of 10 muscles), and prehensio...
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assessment of the hand in tetraplegia using the graded redefined assessment of strength sensibility and Prehension grassp impairment versus function
Topics in Spinal Cord Injury Rehabilitation, 2009Co-Authors: Sukhvinder Kalsiryan, Armin Curt, Michael G Fehlings, Mary C VerrierAbstract:Objective: To refine the Graded and Redefined Assessment of Strength, Sensibility and Prehension (GRASSP) as a measure of upper limb impairment following cervical SCI. Method: A cross-sectional study assessed a cohort of neurologically stable patients with tetraplegia using a preliminary version of the GRASSP. Regression analysis was performed to determine the association between subcomponents of the GRASSP (impairment) and measures of function. The GRASSP was modified based on results. Results: Eliminated static two-point discrimination, tone, and one muscle. Conclusion: The GRASSP Version I consists of Semmes Weinstein monofilaments, manual muscle testing, and qualitative and quantitative Prehension testing.
