Tue, September 14
Speaker: Inge Zijdewind, PhD (University Medical Center Groningen, The Netherlands)
Title: Associated contralateral activity, what can it tell us?
Abstract: During purposely made unilateral contractions the activity is often not confined to the target muscles but also non-target and even contralateral muscles are activated. This contralateral associated activity is non-intentional and often not noticed by the subject. The amount of this associated activity increases with stronger target contractions and increases further with duration of activity.
We studied the pathways of this contralateral associated activity using transcranial magnetic stimulation and fMRI. The data demonstrated that this activity projects to the spinal motoneurons via the ‘normal’ contralateral primary motor cortex and not via an ipsilateral corticospinal projection. Furthermore, the supplementary premotor area is an important secondary motor area involved in the regulation of this associated behavior.
We used this contralateral activity to study how movement is encoded in the motor cortex. In these experiments we changed the hand-position of contralateral hand between experiments while the subject performed the same task; i.e. a 2-minute maximal force with their in index finger in abduction direction. The data that we obtained suggested that the motor system has a strong preference for an organization coded in an external ‘movement-related’ reference frame and less for an organization coded in an internal ‘muscle-related’ reference frame.
Host: Dr. Zev Rymer |
Fri, September 3
Speaker: Nate Bunderson, PhD
Title: Toward Physiologically-based Artificial Limb Control
Abstract: Artificial upper limb control has made great advances in the last decade. While recent developments in multi-functional arms and hands has opened up new possibilities it has also brought to the forefront the difficulties involved in extracting control information from a user and supplying that information to the hardware. In addition to briefly summarizing modern prosthetic control strategies I will give an overview of my work in limb control and discuss how prosthetic control may be enhanced with physiologically-based models. I will discuss one of the most promising methods of control, pattern recognition myoelectric control. We have identified key differences in how novice and experienced users generate EMG patterns during pattern recognition control and hope to focus on these differences during training to achieve efficient control more quickly. I will present a new impulsive virtual prosthesis to facilitate the development of physiologically based controllers. Finally, I will present the immediate problems of a physiologically-based artificial controller and how I intend to use biology's solutions to address them.
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Fri, August 20
Graduate Student Presentations
Speakers: Jennifer Nichols, Derek Miller, and Ian Sharp
Each Graduate student will present 10 minute synopsis of their research (or research plan), followed by 5 minutes of questions. Presentations will focus on: 1) Background to the research question, 2) Hypothesis, and 3) Significance/importance of the research.
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Thur, 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 |
