Thursday, August 5 (10:00am - 11:00am), in Magnuson Auditorium (16th floor)
Speaker: Daniel Ludvig, M.Eng.
Title: Task-Dependent Modulation of Joint Stiffness
Abstract: Joint stiffness defines the dynamic relationship between the position of the joint and torque acting about it; hence it is important in the control of movements and posture. Joint stiffness consists of two components: intrinsic stiffness, which is due to the viscoelastic properties of the joint, muscle, and connective tissue and the inertia of the limb; reflex stiffness, which arises due to the torque produced by the stretch reflex response. Numerous studies have investigated whether subjects can modulate their reflex stiffness voluntarily but have produced contradictory results; a possible reason for this uncertainty is the lack of a proper feedback to provide to subjects. Using intrinsic and reflex stiffness estimates generated by a novel algorithm as feedback, subjects showed the ability to control reflex stiffness independently of intrinsic stiffness. However, when given a task that would be performed optimally by modulating their joint stiffness, subjects produced voluntary torques based on visual feedback, rather than modulating their joint stiffness. These voluntary torques were found to be correlated to the velocity of the visual feedback. Thus, subjects can modulate their joint stiffness is numerous ways—by altering intrinsic stiffness, reflex stiffness or voluntary components. However, it remains to be determined whether there exist tasks, which would motivate subjects to modulate their stiffness in a task-dependent manner.
Host: Eric Perreault |
Fri, July 9
Speaker: Claire Honeycutt, PhD
Title: Effect of cortical stroke on brainstem structures: Preliminary insights from startle induced release of pre-planned movements following stroke
Abstract: Cortical stroke survivors are afflicted with abnormal patterns of muscle activation which limit their ability to perform basic reaching tasks. The neural mechanisms leading to these abnormal movement patterns remain unclear, though it has been suggested that they may reflect an increased reliance on brainstem pathways.
Hence, an understanding of how brainstem function is altered following stroke is important for assessing how they may contribute to motor impairments.
In this study, we investigated brainstem function following stroke using startling acoustic stimuli. In unimpaired individuals, startling acoustic stimuli can trigger the early release of a pre-planned motor action. This phenomenon is often called startReact. Animal and human studies indicate that this early release of planned movement bypasses cortical initiation. Our objective was to quantify the startReact response in stroke patients thereby observing the impact of stroke on brainstem structures related to movement initiation. We evaluated the patterns of activity in 4 arm muscles during voluntary reaching and startReact (reaching initiated by a loud acoustic stimulus) in 4 stroke subjects performing ballistic elbow extension and flexion movements of 25 degrees.
We found that the startReact reflex appears intact when stroke subjects were performing flexion. In contrast, during extension the reflex was impacted by the stroke, specifically the muscle activation patterns were distintive. These results demonstrate that the brainstem mediated reflex of startReact is affected following stroke. However, it is affected differently in extension and flexion tasks.
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Fri, July 2
Speaker: Prof. Pyung-Hun Chang, PhD (KAIST, Korea)
Title: Robust Control of Motion and Impedance of Dual Arms for Asymmetric Bimanual Tasks Using Relative Impedance
Host: Jim Patton
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Thur, July 1 (11:30am - 12:30pm), in 1301
Speaker: Won-Kyung Song, PhD (NRC-Research Institute, Korea)
Title: Rehabilitative and Assistive System Research in the Research Institute of Korea National Rehabilitation Center
Abstract: Korean Ministry of Health and Welfare established the Research Institute
(NRCRI) within National Rehabilitation Center, Seoul, Korea one and half years ago in order to perform rehabilitation research and development projects which can improve the quality of life of Korean with disabilities. NRCRI is engaged in several efforts to develop rehabilitative and assistive devices and systems based on the needs of Korean with disabilities. We investigated what kinds of difficulties they suffer and what Assistive Technologies are needed by conducting a comprehensive survey study and having meetings with persons with diverse disabilities as the first research project. We planned and executed several research and development projects.
Whereas some of them are performed with low or middle technologies, others required high technologies which are used in developing robots, automobile, and airplane. In this presentation our research and development works in the NRCRI will be introduced briefly.
Host: Li-Qun Zhang |
Wed, June 9
Speaker: Lillian Chang, PhD
Title: Capturing and Transferring Human Manipulation Actions
Abstract: Understanding human manipulation can provide insight into strategies for robot manipulators, character animation of hands, and clinical evaluation techniques. In this talk I will present two research projects from my work on analysis and synthesis of manipulation actions. First, to capture accurate human hand shape for example-based methods, we need reliable methods for automatic estimation of anatomic joint parameters. In one application, we have contributed an improved method for determining the joint center of rotation using constrained least-squares optimization. The carefully selected singularity of the mathematical formulation results in an accurate and repeatable solution that is robust to the challenges present in real motion capture of hand joints. Second, human manipulation provides compelling examples of how robots could interact with the environment. We have found that humans use a "pre-grasp interaction" manipulation strategy for grasping heavy or hard-to-reach objects. We have developed a technique for robot pre-grasp interaction and have demonstrated that this strategy improves the robot's effective functionality for reaching and transporting household objects.
Host: Sandro Mussa-Ivaldi
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Fri, June 11
Speaker: Robert Scheidt, PhD
Title: Reorganization of coordination among redundant control signals during adaptation to rotation and scaling distortions of a newly learned sensorimotor transformation
Abstract: Neuromotor control is inherently redundant in that a vast number of efferent signals influence the low-dimensional, dynamic behavior of the body. An important unanswered question in the study of goal-directed movements is how the brain learns to coordinate changes within the set of redundant control parameters (eg. motor cortical activities, spinal stretch reflex thresholds, muscle forces, joint torques, etc.) to produce desired changes in the state of a controlled endpoint (eg. hand kinematics and/or kinetics). We are addressing this question in a series of experiments wherein subjects wear a data glove instrumented with a large number of bend sensors. Signals from these sensors drive motion of a cursor on a computer screen via a linear hand-to-screen projection matrix: Each hand configuration projects onto only one screen location, but each screen location can be achieved using an infinite number of hand configurations. Subjects capture screen targets with the cursor by forming gestures with the fingers. This task is unique in that the hand-to-screen projection operator establishes a clear separation between control degrees of freedom contributing to kinematic performance and those that do not.
Previous experiments using this approach found that when subjects receive real-time visual feedback of cursor motion, they learn how spatial relationship between screen targets may be used to constrain the choice of hand postures. This learning generalized beyond regions of the screen workspace explored during training, allowing subjects to successfully acquire new targets, Practicing the target capture task induced the formation of finger coordination patterns such that motion in degrees of freedom not contributing to cursor motion was reduced. These observations provide compelling evidence that subjects learned an inverse of the hand-to-screen mapping, thereby learning a 'motor representation' of the Euclidean space onto which finger movements were mapped.
Here we present recent experiments assessing the stability of these newly-learned coordination patterns when the nominal hand-to-screen mapping is distorted through application of a simple scaling or rotation transformation of cursor motion on the screen. We sought to revisit the hypothesis that the brain processes errors in movement direction and extent separately and in computationally distinct ways during learning (Bock, 1992; Krakauer et al., 2000; Vindras et al, 2005). Specifically we tested whether extent errors induce learning of a single gain factor applied globally across all movement directions and extents whereas direction errors induce learning of ‘rotation parameters’ that only generalize to movements of different extent made in the trained direction (Krakauer et al., 2000).
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Fri, May 21
Speaker: Shailesh Kantak, PhD (Postdoctoral Candidate)
Title: Neural substrates of motor memory consolidation: A double dissociation of primary motor cortex and dorsolateral prefrontal cortex induced by practice structure
Abstract: Motor practice drives subsequent offline activity within functionally related resting brain networks. Little is known about how offline neural networks are modulated by practice structures known to affect motor skill learning. To investigate the neural correlates of motor memory consolidation, we applied 1 Hz repetitive Transcranial Magnetic Stimulation (rTMS) immediately after a bout of constant or variable motor practice to disrupt either primary motor cortex (M1) or dorsolateral prefrontal cortex (DLPFC), two putative nodes previously shown to be engaged in early consolidation. Motor learning was assessed the following day through a performance-based retention test. Immediately after constant practice, rTMS to M1, but not DLPFC attenuated retention of the motor skill. In contrast, immediately after variable practice, rTMS to DLPFC, but not M1 attenuated retention performance. These findings provide evidence that for motor skills, the neural substrates of motor memory consolidation are modulated by practice structure.
Host: Jim Stinear
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Wed, May 19
Speaker: Art Kuo, PhD
Title: Patients are from mars, robots are from venus: How to win effort and influence rehabilitation
Abstract: I will present my own skewed view of different rehabilitation strategies, and how many seem not to provide exercise with appropriate specificity, proper feedback, or incentive to participate effectively. I propose an approach that attempts to provide a short-term incentive for subjects to participate in exercise, toward some desired long-term goal. Key to providing incentive is the evaluation of a person's preferred means of executing a motor task. Once that preference is known, it is then possible to design a variation of the task to cause that preference to shift, ideally in alignment with a long-term rehabilitation goal. I will present some preliminary data showing how this might work.
Host: Derek Kamper
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Fri, May 14
Speaker: Felix Huang, PhD
Complete Abstract for Movement amplification in manual skill training
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Wed, May 5
Speaker: Cliff Klein, PhD (Postdoctoral Candidate)
Complete Abstract for Relative contributions of activation impairment and muscle atrophy to dorsiflexor weakness in chronic stroke survivors
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Mon, May 3 (2:30pm - 3:30pm), in 1301
Speaker: Xun Niu, PhD (Postdoctoral Candidate)
Complete Abstract for Multi-finger Prehension Synergy: Stability and Inverse Optimization
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Wed, April 28 (1:00pm - 2:00pm), in 1301
Speaker: Heather Hayes, PhD (Postdoctoral Candidate)
Complete Abstract for Sensory processing in a walking spinal cord
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Tue, April 27 (11:00am - 12:00pm), in 1301
Speaker: Ganesh Gowrishankar, PhD (ATR Computational Neuroscience Laboratories, Kyoto, Japan)
Complete Abstract for Mechanisms of motor learning: in humans, for robots
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Mon, April 26
Speaker: Avi Barliya
Complete Abstract for Control strategies revealed through representations
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Fri, April 23 (10:00am - 11:00am), in 1301
Speaker: Minos Niu (Postdoctoral Candidate)
Complete Abstract for How position and velocity information from proprioception is used in controlling arm movements
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Fri, April 16
Speaker: Nupur Hajela, PT (Postdoctoral Candidate)
Complete Abstract for Evoked Human Cutaneous Reflexes during Standing and Step Initiation
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Mon, April 5 (2:30pm - 3:30pm), in 1301
Speaker: Qi Shao, PhD (Postdoctoral Candidate)
Complete Abstract for seminar EMG-driven modeling and its application in simulating rehabilitation
Host: Mehdi Mirbagheri |
Fri, March 26
Speaker: Max Berniker, Ph.D.
Complete Abstract for seminar Learning Priors for Bayesian Computations
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Fri, March 26 (8:30am - 9:30am), in 1301
Speaker: Vengateswaran J. Ravichandran (PhD Candidate)
Complete Abstract for seminar Role of long latency responses to stretch during control of posture and prior to movement onset
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Mon, March 22 (9am - 10am), in 1301
Speaker: James Finley (PhD Candidate)
Complete Abstract for seminar Regulation of Feed-Forward and Feedback Contributions to Ankle Stability during Balance Tasks
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Fri, March 12
Speaker: Veronica Santos, Ph.D. (Arizona State University)
Complete Abstract for seminar Towards enhanced functionality of artificial hands
Host: Wendy Murray
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Wed, Jan 13 (12:30pm-1:30pm)
Speaker: Matteo Bertucco, PhD (Postdoctoral Candidate)
Complete Abstract for seminar Is there a planning control following Fitts’ law? The timing of anticipatory postural adjustments follows Fitts’ law for step initiation.
Host: Dr. Zev Rymer
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