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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 Journal of Mathematical Psychology Abbreviated Journal (up)  
  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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  Call Number Serial 70  
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Author Harel Arzi; Tal Krasovsky; Moshe Pritsch; Dario G. Liebermann doi  openurl
  Title Movement control in patients with shoulder instability: a comparison between patients after open surgery and nonoperated patients Type Journal Article
  Year 2014 Publication Journal of Shoulder and Elbow Surgery Abbreviated Journal (up)  
  Volume 23 Issue 7 Pages 982–992  
  Keywords Smoothness; kinesthesis; arm kinematics; shoulder instability; open surgery  
  Abstract Background

Open surgery to correct shoulder instability is deemed to facilitate recovery of static and dynamic motor functions. Postoperative assessments focus primarily on static outcomes (e.g., repositioning accuracy). We introduce kinematic measures of arm smoothness to assess shoulder patients after open surgery and compare them with nonoperated patients. Performance among both groups of patients was hypothesized to differ. Postsurgery patients were expected to match healthy controls.

Methods

All participants performed pointing movements with the affected/dominant arm fully extended at fast, preferred, and slow speeds (36 trials per subject). Kinematic data were collected (100 Hz, 3 seconds), and mixed-design analyses of variance (group, speed) were performed with movement time, movement amplitude, acceleration time, and model-observed similarities as dependent variables. Nonparametric tests were performed for number of velocity peaks.

Results

Nonoperated and postsurgery patients showed similarities at preferred and faster movement speeds but not at slower speed. Postsurgery patients were closer to maximally smoothed motion and differed from healthy controls mainly during slow arm movements (closer to maximal smoothness, larger movement amplitude, shorter movement time, and lower number of peaks; i.e., less movement fragmentation).

Conclusions

Arm kinematic analyses suggest that open surgery stabilizes the shoulder but does not necessarily restore normal movement quality. Patients with recurrent anterior shoulder instability (RASI) seem to implement a “safe” but nonadaptive mode of action whereby preplanned stereotypical movements may be executed without depending on feedback. Rehabilitation of RASI patients should focus on restoring feedback-based movement control. Clinical assessment of RASI patients should include higher order kinematic descriptors.
 
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  Call Number Serial 74  
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Author Liebermann, D.G.; Levin, M.F.; McIntyre, J.; Weiss, P.L.; Berman, S. url  doi
openurl 
  Title Arm path fragmentation and spatiotemporal features of hand reaching in healthy subjects and stroke patients Type Journal Article
  Year 2010 Publication Conference Proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference Abbreviated Journal (up) Conf Proc IEEE Eng Med Biol Soc  
  Volume 2010 Issue Pages 5242-5245  
  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  
  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.  
  Address Physical Therapy Dept., Sackler Faculty of Medicine, Tel Aviv University, 69978 Israel. dlieberm@post.tau.ac.il  
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  ISSN 1557-170X ISBN Medium  
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  Notes PMID:21096047 Approved no  
  Call Number Serial 30  
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Author Liebermann, D.G.; Biess, A.; Friedman, J.; Gielen, C.C.A.M.; Flash, T. pdf  url
doi  openurl
  Title Intrinsic joint kinematic planning. I: reassessing the Listing's law constraint in the control of three-dimensional arm movements Type Journal Article
  Year 2006 Publication Experimental Brain Research Abbreviated Journal (up) Exp Brain Res  
  Volume 171 Issue 2 Pages 139-154  
  Keywords Adolescent; Adult; Analysis of Variance; *Arm; Biomechanics; Eye Movements/*physiology; Humans; Joints/*physiology; Male; Movement/*physiology; *Musculoskeletal System; Orientation/*physiology; Posture  
  Abstract This study tested the validity of the assumption that intrinsic kinematic constraints, such as Listing's law, can account for the geometric features of three-dimensional arm movements. In principle, if the arm joints follow a Listing's constraint, the hand paths may be predicted. Four individuals performed 'extended arm', 'radial', 'frontal plane', and 'random mixed' movements to visual targets to test Listing's law assumption. Three-dimensional rotation vectors of the upper arm and forearm were calculated from three-dimensional marker data. Data fitting techniques were used to test Donders' and Listing's laws. The coefficient values obtained from fitting rotation vectors to the surfaces described by a second-order equation were analyzed. The results showed that the coefficients that represent curvature and twist of the surfaces were often not significantly different from zero, particularly not during randomly mixed and extended arm movements. These coefficients for forearm rotations were larger compared to those for the upper arm segment rotations. The mean thickness of the rotation surfaces ranged between approximately 1.7 degrees and 4.7 degrees for the rotation vectors of the upper arm segment and approximately 2.6 degrees and 7.5 degrees for those of the forearm. During frontal plane movements, forearm rotations showed large twist scores while upper arm segment rotations showed large curvatures, although the thickness of the surfaces remained low. The curvatures, but not the thicknesses of the surfaces, were larger for large versus small amplitude radial movements. In conclusion, when examining the surfaces obtained for the different movement types, the rotation vectors may lie within manifolds that are anywhere between curved or twisted manifolds. However, a two-dimensional thick surface may roughly represent a global arm constraint. Our findings suggest that Listing's law is implemented for some types of arm movement, such as pointing to targets with the extended arm and during radial reaching movements.  
  Address Department of Physical Therapy, Sackler Faculty of Medicine, Tel-Aviv University, 69978, Ramat Aviv, Israel. dlieberm@post.tau.ac.il  
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  ISSN 0014-4819 ISBN Medium  
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  Notes PMID:16341526 Approved no  
  Call Number Penn State @ write.to.jason @ Serial 18  
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Author Liebermann, D.G.; Defrin, R. url  doi
openurl 
  Title Characteristics of the nociceptive withdrawal response elicited under aware and unaware conditions Type Journal Article
  Year 2009 Publication Journal of Electromyography and Kinesiology : Official Journal of the International Society of Electrophysiological Kinesiology Abbreviated Journal (up) J Electromyogr Kinesiol  
  Volume 19 Issue 2 Pages e114-22  
  Keywords Adult; Arm/*physiopathology; Attention; *Awareness; Cues; Female; Humans; Male; Movement; *Muscle Contraction; Muscle, Skeletal/*physiopathology; Pain/*physiopathology; *Reflex; *Startle Reaction  
  Abstract 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.  
  Address 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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  Series Volume Series Issue Edition  
  ISSN 1050-6411 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:18063387 Approved no  
  Call Number Serial 34  
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