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Author |
Biess, A.; Liebermann, D.G.; Flash, T. |
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Title  |
A computational model for redundant human three-dimensional pointing movements: integration of independent spatial and temporal motor plans simplifies movement dynamics |
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Journal Article |
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Year |
2007 |
Publication |
The Journal of Neuroscience : the Official Journal of the Society for Neuroscience |
Abbreviated Journal |
J Neurosci |
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Volume |
27 |
Issue |
48 |
Pages |
13045-13064 |
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Keywords |
Analysis of Variance; Arm/physiology; Biomechanics; *Computer Simulation; Humans; *Models, Biological; Movement/*physiology; *Nonlinear Dynamics; Posture/physiology; Psychomotor Performance/*physiology; Range of Motion, Articular/physiology; Reaction Time/physiology; Space Perception/*physiology; Time Factors; Torque |
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Abstract |
Few computational models have addressed the spatiotemporal features of unconstrained three-dimensional (3D) arm motion. Empirical observations made on hand paths, speed profiles, and arm postures during point-to-point movements led to the assumption that hand path and arm posture are independent of movement speed, suggesting that the geometric and temporal properties of movements are decoupled. In this study, we present a computational model of 3D movements for an arm with four degrees of freedom based on the assumption that optimization principles are separately applied at the geometric and temporal levels of control. Geometric properties (path and posture) are defined in terms of geodesic paths with respect to the kinetic energy metric in the Riemannian configuration space. Accordingly, a geodesic path can be generated with less muscular effort than on any other, nongeodesic path, because the sum of all configuration-speed-dependent torques vanishes. The temporal properties of the movement (speed) are determined in task space by minimizing the squared jerk along the selected end-effector path. The integration of both planning levels into a single spatiotemporal representation simplifies the control of arm dynamics along geodesic paths and results in movements with near minimal torque change and minimal peak value of kinetic energy. Thus, the application of Riemannian geometry allows for a reconciliation of computational models previously proposed for the description of arm movements. We suggest that geodesics are an emergent property of the motor system through the exploration of dynamical space. Our data validated the predictions for joint trajectories, hand paths, final postures, speed profiles, and driving torques. |
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Department of Mathematics, Weizmann Institute of Science, 76100 Rehovot, Israel. armin.biess@weizmann.ac.il |
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0270-6474 |
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PMID:18045899 |
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35 |
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Author |
Liebermann, D.G.; Levin, M.F.; McIntyre, J.; Weiss, P.L.; Berman, S. |
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Title |
Arm path fragmentation and spatiotemporal features of hand reaching in healthy subjects and stroke patients |
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Journal Article |
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Year |
2010 |
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Conference Proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference |
Abbreviated Journal |
Conf Proc IEEE Eng Med Biol Soc |
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2010 |
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5242-5245 |
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Keywords |
Aged; Aged, 80 and over; Analysis of Variance; Arm/*physiology; Biomechanics/physiology; Female; Hand/*physiology; *Health; Humans; Male; Middle Aged; Movement/*physiology; Posture/physiology; Principal Component Analysis; Stroke/*physiopathology; Time Factors |
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Abstract |
Arm motion in healthy humans is characterized by smooth and relatively short paths. The current study focused on 3D reaching in stroke patients. Sixteen right-hemiparetic stroke patients and 8 healthy adults performed 42 reaching movements towards 3 visual targets located at an extended arm distance. Performance was assessed in terms of spatial and temporal features of the movement; i.e., hand path, arm posture and smoothness. Differences between groups and within subjects were hypothesized for spatial and temporal aspects of reaching under the assumption that both are independent. As expected, upper limb motion of patients was characterized by longer and jerkier hand paths and slower speeds. Assessment of the number of sub-movements within each movement did not clearly discriminate between groups. Principal component analyses revealed specific clusters of either spatial or temporal measures, which accounted for a large proportion of the variance in patients but not in healthy controls. These findings support the notion of a separation between spatial and temporal features of movement. Stroke patients may fail to integrate the two aspects when executing reaching movements towards visual targets. |
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Physical Therapy Dept., Sackler Faculty of Medicine, Tel Aviv University, 69978 Israel. dlieberm@post.tau.ac.il |
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1557-170X |
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PMID:21096047 |
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30 |
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Merdler, T.; Liebermann, D.G.; Levin, M.F.; Berman, S. |
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Title |
Arm-plane representation of shoulder compensation during pointing movements in patients with stroke |
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Journal Article |
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2013 |
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Journal of Electromyography and Kinesiology : Official Journal of the International Society of Electrophysiological Kinesiology |
Abbreviated Journal |
J Electromyogr Kinesiol |
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23 |
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4 |
Pages |
938–947 |
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Keywords |
Kinematics; Arm movement; Rehabilitation |
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Improvements in functional motor activities are often accompanied by motor compensations to overcome persistent motor impairment in the upper limb. Kinematic analysis is used to objectively quantify movement patterns including common motor compensations such as excessive trunk displacement during reaching. However, a common motor compensation to assist reaching, shoulder abduction, is not adequately characterized by current motion analysis approaches. We apply the arm-plane representation that accounts for the co-variation between movements of the whole arm, and investigate its ability to identify and quantify compensatory arm movements in stroke subjects when making forward arm reaches. This method has not been previously applied to the analysis of motion deficits. Sixteen adults with right post-stroke hemiparesis and eight healthy age-matched controls reached in three target directions (14 trials/target; sampling rate: 100Hz). Arm-plane movement was validated against endpoint, joint, and trunk kinematics and compared between groups. In stroke subjects, arm-plane measures were correlated with arm impairment (Fugl-Meyer Assessment) and ability (Box and Blocks) scores and were more sensitive than clinical measures to detect mild motor impairment. Arm-plane motion analysis provides new information about motor compensations involving the co-variation of shoulder and elbow movements that may help to understand the underlying motor deficits in patients with stroke. |
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Department of Industrial Engineering and Management, Ben-Gurion University of the Negev, Beer-Sheva, Israel |
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1050-6411 |
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PMID:23566477 |
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69 |
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Author |
Liebermann, D.G.; Defrin, R. |
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Characteristics of the nociceptive withdrawal response elicited under aware and unaware conditions |
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Journal Article |
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2009 |
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Journal of Electromyography and Kinesiology : Official Journal of the International Society of Electrophysiological Kinesiology |
Abbreviated Journal |
J Electromyogr Kinesiol |
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19 |
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2 |
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e114-22 |
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Adult; Arm/*physiopathology; Attention; *Awareness; Cues; Female; Humans; Male; Movement; *Muscle Contraction; Muscle, Skeletal/*physiopathology; Pain/*physiopathology; *Reflex; *Startle Reaction |
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BACKGROUND: Nociceptive withdrawal reflexes (NWR) are subject to supraspinal modulation. Therefore, awareness about a noxious stimulation may affect its characteristics. The goal of this study was to investigate the effect of different degrees of awareness on the NWR. METHOD: Eight subjects performed back and forth hand movements from a common starting point towards four visual targets during which NWR was evoked when subjects were either unaware or aware of a noxious stimulation (unaware-NWR and aware-NWR). For the comparison between the NWR under both conditions, onset latencies and kinematic variables were computed respectively from the recorded Biceps Brachii EMG and from the spatial coordinates of hand reflective markers. RESULTS: The onset latency of unaware-NWR (mean+/-SD 73.9+/-13 ms) was significantly shorter than that of the aware-NWR (91.1+/-27 ms, p<0.05). The total duration of the muscular activation was shorter in unaware-NWR than in aware-NWR. The slopes of the tangential velocity-time curves were steeper for unaware-NWR than for aware-NWR (p=0.057). CONCLUSIONS: The results suggest that supraspinal regulation of NWR under different degrees of awareness involves the re-parameterization of selected spatiotemporal aspects of a pre-structured motor response. |
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Department of Physical Therapy, The Stanley Steyer School of Health Professions, Sackler Faculty of Medicine, Tel-Aviv University, Ramat Aviv, Tel Aviv 69978, Israel |
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1050-6411 |
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PMID:18063387 |
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34 |
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Author |
Levin, M.F.; Liebermann, D.G.; Parmet, Y.; Berman, S. |
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Title |
Compensatory Versus Noncompensatory Shoulder Movements Used for Reaching in Stroke |
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Journal Article |
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2015 |
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Neurorehabilitation and Neural Repair |
Abbreviated Journal |
Neurorehabil Neural Repair |
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adaptation; arm movement; compensation; kinematics; recovery; rehabilitation |
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BACKGROUND: The extent to which the upper-limb flexor synergy constrains or compensates for arm motor impairment during reaching is controversial. This synergy can be quantified with a minimal marker set describing movements of the arm-plane. OBJECTIVES: To determine whether and how (a) upper-limb flexor synergy in patients with chronic stroke contributes to reaching movements to different arm workspace locations and (b) reaching deficits can be characterized by arm-plane motion. METHODS: Sixteen post-stroke and 8 healthy control subjects made unrestrained reaching movements to targets located in ipsilateral, central, and contralateral arm workspaces. Arm-plane, arm, and trunk motion, and their temporal and spatial linkages were analyzed. RESULTS: Individuals with moderate/severe stroke used greater arm-plane movement and compensatory trunk movement compared to those with mild stroke and control subjects. Arm-plane and trunk movements were more temporally coupled in stroke compared with controls. Reaching accuracy was related to different segment and joint combinations for each target and group: arm-plane movement in controls and mild stroke subjects, and trunk and elbow movements in moderate/severe stroke subjects. Arm-plane movement increased with time since stroke and when combined with trunk rotation, discriminated between different subject groups for reaching the central and contralateral targets. Trunk movement and arm-plane angle during target reaches predicted the subject group. CONCLUSIONS: The upper-limb flexor synergy was used adaptively for reaching accuracy by patients with mild, but not moderate/severe stroke. The flexor synergy, as parameterized by the amount of arm-plane motion, can be used by clinicians to identify levels of motor recovery in patients with stroke. |
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1545-9683 |
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PMID:26510934 |
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79 |
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