2014 Research Seminars - Rehabilitation Institute of Chicago

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2014 Research Seminars 

Fri. Dec 12

Speaker: Camila Shirota

Title: Towards Effective Fall Prevention Mechanisms in Lower-Limb Prostheses: Trip Recovery in Transfemoral Amputees

Abstract:  Transfemoral (above-knee) amputees are prone to falling, indicating that current prevention methods are lacking. Microprocessor-controlled and powered prostheses could improve responses to perturbations, but prosthetic responses that facilitate balance recovery are unclear. Trips in able-bodied subjects elicit stereotypical movement patterns (recovery strategies) related to perturbation timing throughout swing phase; however, which strategy to use in response to a specific perturbation is poorly understood. Further, knowledge of the effects of amputation on trip recovery is limited. Identification of the user’s intention, to coordinate the prostheses’ response, has yet to be studied throughout swing phase. This dissertation aims at understanding how amputees attempt recovering from trips, and proposes a method to automatically identify their intended strategy during recovery.

A custom-made device tripped able-bodied and transfemoral amputee subjects multiple times throughout swing phase during treadmill walking. Data collected included motion of the pelvis and lower-limbs, and muscle activity (EMG) from both legs. Kinematic patterns of the tripped foot from trip to foot-strike were used to sort recovery strategies. Linear discriminant analysis classifiers were used to detect trips and identify recovery strategies in able-bodied subjects and the prosthesis side of transfemoral amputees using tripped limb kinematic data, tripped thigh EMG, or fusion (combined) data.

In able-bodied subjects, perturbation duration did not affect initial strategy selection, but could force a switch between strategies. Transfemoral amputees used typical able-bodied and amputee-specific (hopping and skipping) strategies. Patterns of recovery in able-bodied subjects were less similar to responses on the sound side than on the prosthesis side. Using fusion data to classify strategies resulted in low and least variable errors across subjects.

This dissertation sets the foundation for real-time trip recovery mechanisms in transfemoral prostheses. It supports that typical able-bodied strategies could potentially avoid falls from prosthesis side trips, as they align with amputees’ intent. The 50ms classification delay is similar to latencies of able-bodied responses and should allow effective prosthesis responses. Further, recovery from sound side trips should be addressed, as it was restricted by the prosthesis’ limited ability to count-act the perturbation. This dissertation’s framework could be used to investigate recovery from other types of perturbations.

Host: Dr. Kuiken

Fri. Dec 12 

Speaker: Christine Thomas

Title: Motoneuron death after human spinal cord injury: how does it impact recovery of muscle function?

Abstract:  Death of spinal motoneurons is well accepted in diseases like amyotrophic lateral sclerosis, and poliomyelitis. Far less attention is given to motoneuron death after human spinal cord injury even though denervation makes significant contributions to muscle atrophy, weakness and dysfunction. These changes make it important to examine the extent of motoneuron death after human spinal cord injury at different levels, to understand how disruption of spinal circuitry impacts the excitability of surviving motoneurons, and to assess the consequent changes in muscle use.

Host: Drs. Suresh / Rymer

Fri. Dec 5

Speaker: Debjani Mukherjee

Title: Ethics and the Researcher-Participant Relationship

Thur. Dec 4

Speaker: Mohamad Parnianpour

Title: Quantitative Trunk Performance as inspired by Biomechanical Modeling

Abstract:  The challenge of trunk assessment is that we are deprived of comparing the injured or disabled one with the healthy counterpart, which has motivated many to understand the normal function and limits of capacity along elemental bases of performance. Concepts such as strength, endurance, coordination, steadiness, controllability, and stability have been studied in hope that these results could bring us closer to identifying risk factors, understanding injury mechanisms, and guide us towards prevention and rehabilitation in a unified paradigm.
Examples will be provided to encourage a multi-disciplinary dialogue for future research.

Host: Dr. Kamper

Tue. Dec 2

Speaker: Adam Charles

Title: Robust Tracking of High-Dimensional Signals

Abstract: Dynamic filtering is a classic problem in many applications where one must merge noisy measurements and a dynamics model to accurately infer a time-varying signal. Classically, dynamic filtering methods excel in estimating low-dimensional vectors with Gaussian statistics. Many applications, however, require algorithms that can operate efficiently on very high-dimension signals that have significant additional structure (e.g., dynamic MRI). One such structure that has led to state-of-the-art techniques for high-dimensional signals is sparsity. Sparse signals are assumed to be composed of a linear combination of just a few elements taken from a large dictionary.

Host: Dr. Kording

Fri. Nov 21 

Speaker:  Lois Huggins and Kathy Galvin

Title: Managing Interpersonal Relationships

Host: Dr. Kuiken

Fri. Nov 14

Speaker: Kai Qian

Title: Incorporation of natural sensory feedback to improve control of a brain-machine interface for grasp

Abstract: Manipulation of objects is a fundamental part of the human experience, whether performing activities of daily living such as eating or dressing, expressing ourselves creatively through music or art, or, increasingly, communicating. We interact with our environment primarily through our hands. Unfortunately, motor control of the hands can be severely compromised by a variety of neuromuscular conditions such as spinal cord injury, amyotrophic lateral sclerosis, or muscular dystrophy, with a devastating impact on function and lifestyle. Efforts have been made to try to restore some of the lost function through the use of cortical signals to control external devices. These brain-machine interfaces have recently been implemented in human subjects to enable control of computers or robots. Manipulation of objects, however, remains rather awkward, in large part due to the limited sensory feedback between the external device and the user. In natural grasping, humans are highly reliant on the exquisite sensory information from the hand to properly perform tasks. This is lost with use of a robot, even though many individuals with motor hand impairment might have substantial sparing of sensory information. We propose to utilize this rich sensory feedback by having the individual’s own hand make contact and manipulate the object through the use of a hand exoskeleton that is controlled via populations of cortical neurons. The individual will be fully integrated into the activity, with the exoskeleton providing actuation and the individual’s own hand providing sensation. We will test the efficacy of such a system in non-human primates.

Host: Dr. Kamper

Wed. Nov 12 

Speaker: Geeske Peeters, PhD

Title 1: The influence of long-term exposure and timing of physical activity on new joint pain and stiffness in mid-age women

Abstract: Physical activity is a potential target for interventions to delay the onset of osteoarthritis. The aim was to examine the influence of long-term exposure and timing of physical activity (PA) on new joint pain/stiffness in mid-age women. We used data from 5105 participants (born 1946-51) in the Australian Longitudinal Study on Women’s Health who completed survey items on PA (1998, 2001 and 2004) and joint pain/stiffness (2007 and 2010). Associations were analysed using logistic regression, with separate models for the cumulative model (i.e. PA is summed over the 3 surveys), the sensitive periods model (i.e. PA measured at each survey in one regression model) and the critical periods model (i.e. separate regression models for PA at each survey). In 2007/2010, 951 (18.6%) participants reported new-onset joint pain/stiffness. In all three models, PA was associated with a lower risk of joint symptoms; however, the model fit was better for the sensitive periods than the cumulative or critical periods models. We therefore concluded that in mid-age women, physical activity between the ages 47 and 58 was associated with a lower risk of joint pain/stiffness nine years later. Associations were stronger for PA in the last six years than for earlier PA.

Title 2: Long-term consequences of falls on wellbeing in older women

Abstract: Wellbeing is an important outcome in clinical trials, but the long-term consequences of falls on wellbeing in an ageing population are unclear. The aim was to investigate the long-term consequences of falls on wellbeing in community-dwelling older women. Using data from 10,277 participants (mean age 75 ±1.5) in the Australian Longitudinal Study on Women’s Health who returned surveys in 1999, 2002, 2005, 2008 and 2011, we compared fallers and non-fallers on each of the Short Form-36 subscales (range 0-100) using linear mixed modelling. Over 12 years, 46.7% reported at least one fall. The fallers scored significantly lower than the non-fallers on all subscales (p<0.001) except ‘role emotional’. The differences in scores ranged from -7.2 (95% confidence interval [CI] -9.3, -5.2) for ‘role physical’ to -1.1 (CI -1.7, -0.4) for ‘mental health’. The declines in scores over time were greater for fallers than non-fallers and this increased decline was apparent up to 6 years before the first fall. In conclusion, in older women, fallers have lower wellbeing for all domains than non-fallers. The gap in wellbeing emerges years before the first fall occurs and continues to increase after the fall.

Host: Dr. de Bruin

Fri. Nov 7

Speaker: Marcia O'Malley, PhD, Associate Professor in the Dept of Mech Eng and Materials Science at Rice University

Title:  Techniques for Active User Engagement in Robotic Rehabilitation

Abstract: The Mechatronics and Haptic Interfaces Lab at Rice University has been developing robotic devices, objective assessments, and control architectures for upper extremity rehabilitation robots employed after stroke and incomplete spinal cord injury. In this talk, a range of techniques for ensuring active engagement of the participant in therapeutic interventions with robotic devices will be discussed. Objective measures of motor impairment can provide frequent feedback to the participant regarding their performance during therapy. Control architectures can require initiation or sustained input from the user in order to generate desired movements. Further, controllers can be designed to adapt to the user’s changing capabilities, which may be dependent on position or direction of movement. Results from a variety of ongoing clinical evaluations will be discussed in relation to these topics. These research efforts embody the collaborative, interdisciplinary nature of my group’s research in biorobotics, haptics, neural engineering, and robotic rehabilitation.

Host: Dr. Argall

Fri, Oct 31

Speaker: Stephen Ellis, PhD

Title: The Misalignment Effect Function, communication delay and Fitts' Law

Abstract:  Using a Fitts'-like 3D reaching task and a wide variety of rotations and targets in a high fidelity virtual environment, we have recently made the most accurate, generalized measurement of the effect of misalignment between users’ display and control reference frames. Such misalignment arise often during teleoepration. We call the function we have measured the Misalignment Effect Function (MEF) and haves determined it about canonical rotation axes, e.g. pure pitch, roll or yaw, as well as for axes oblique with respect to an operator's body.

We have used our analysis of the MEF to illustrate what may be a new law of human motion and to determine a natural measure of control difficulty which we show is related to the Fitts' Index of Difficulty (ID). This relation is evident from our studies of the interaction of system latency and control difficulty produced by misalignment. Our study of these two factors has revealed a pure multiplicative statistical interaction between them which we show is closely related to an earlier interaction between latency and the Fitts' ID itself reported by Hoffmann. Our replication of his work points to a simple technique to generalize latency requirements for manipulative user interfaces such as found in manual telerobotics. Our work also shows how high fidelity virtual environments can be used to conduct research that could be impractical if done with conventional equipment.

Host: Dr. Patton

Thurs, Oct 23

Speaker: Jason Kutch, PhD, Asst Prof., BME, University of Southern California

Title: The muscle synergies you didn't know you have: cortical coordination of pelvic floor and lower limb muscles

Abstract:  Human pelvic floor muscles (PFM) have been shown to operate synergistically with a wide variety of non-pelvic floor muscles of the trunk and lower limbs, which has been suggested to be an important contributor to continence and pelvic stability during functional tasks. Despite the potential relevance of PFM synergies to prevalent clinical conditions, including incontinence and chronic pelvic pain, the neural centers responsible for these synergies are poorly understood. Here we use a multimodal approach - including electromyography, functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), and sonographic imaging - to localize the neural centers generating PFM synergies. We first use electromyographic recordings to extend previous findings and demonstrate that pelvic floor muscles activate synergistically during voluntary activation of gluteal muscles. We then show, using fMRI, that a region of the medial wall of the precentral gyrus consistently activates during both voluntary pelvic floor muscle activation and voluntary gluteal activation. We finally confirm, using TMS, that the fMRI-identified medial wall region likely generates pelvic floor muscle activation. We generalize these findings to a similar synergy between the PFM and toe muscles, and show that the coordination of the PFM with trunk and lower limb muscles likely involves two distinct regions in the medial wall of the precentral gyrus. We conclude by showing how these results are critical in understanding the neural mechanism of chronic pelvic pain in women and men.

Please see also:
Asavasopon S, Rana M, Kirages DJ, Yani MS, Fisher BE, Hwang DH, Lohman EB, Berk LS, Kutch JJ (2014) Cortical Activation Associated with Muscle Synergies of the Human Male Pelvic Floor. The Journal of Neuroscience 34:13811-13818. http://www.jneurosci.org/content/34/41/13811.short 

Host: Dr. Rymer

Fri, Oct 17

Speaker: Stephen Coombes, PhD

Title: Neuroanatomical basis of error augmentation in chronic stroke

Abstract: Augmenting visual error to improve motor control and motor learning is well established in healthy adults. In the first section of the talk I will present functional neuroimaging data that characterizes the brain circuits that underlie error augmentation in healthy adults. In the second section of the talk I will build on this line of work by presenting data which shows that augmenting visual error improves motor control in the chronic phase after stroke, and that the brain circuits involved are not identical to those in healthy adults. In the third section of the talk I will present diffusion MRI data which show that the behavioral effects of error augmentation after stroke can be predicted by the structural integrity of specific brain regions.

Host: Dr. Patton

Fri, Oct 3 

Speaker: Claire Honeycutt, PhD

Title: Expanding our understanding of the brainstem’s role in movement: a perspective from cat to human

Abstract: While it is well established that the brainstem plays an important role in movement control, the specific role of this structure remains uncertain. Much of what we know about the brainstem contribution to movement comes from the seminal work by Lawrence and Kuypers which concluded that the brainstem (reticulospinal) and cortex (corticospinal) tracts exist within a proximal-distal gradient that defines their influence. Recent work has expanded and challenged this strict framework. The objective of this talk is to highlight our new understanding of how the brainstem contributes to

  1. whole-body balance control,
  2. hand movement, and
  3. movement planning following stroke.

First, we evaluated the capacity of the brainstem and spinal cord to generate key features of the balance response. While it has long been established that the brainstem is involved in whole-body balance control, the specific contributions were unclear. We found that these structures could generate appropriately directed muscular activation. Second, the startle reflex, which is mediated by the reticulospinal tract, was utilized as a non-invasive probe of movement planning to evaluate if reticulospinal connections exist to the muscles of the hand in humans. It was found that the reticulospinal tract likely has connections to the intrinsic muscles of the hand in humans but its functional role is limited to coordinated movement of the whole hand. Finally, the startle reflex was utilized to probe the ability of stroke survivors to plan movement. It was found that planned movements initiated in stroke survivors by a startle stimulus were not statistically different from movements in unimpaired individuals in terms of onset latency and muscle activation patterns opening up this reflex as a potential therapeutic target. In conclusion, these results point to an updated and expanded view of the brainstem’s role in movement control, though it is certain that all levels of the nervous system work in parallel to generate a large repertoire of diverse, coordinated movements throughout the whole body. 

Host: Dr. Perreault

Fri, Sept 19

Speaker: Mark Segraves, PhD

Title: Cortical Control of Gaze while Searching Natural Scenes

Abstract: We use the rhesus monkey model to address questions concerning the cognitive control of eye movement behavior. Our overall goal is to understand how the brain controls where we look. To accomplish this, it’s important to study brain activity and behavior under conditions that approximate those in the real world. The frontal eye field (FEF) is the cortical area most closely involved in the control of purposive voluntary eye movements. We have recorded FEF neuron activity while monkeys looked at images of natural scenes, and found that it was related to planning upcoming eye movements, as well as being sensitive to salient visual features of the image. In parallel with the development of our understanding of how the brain controls eye movements, there have been substantial advances in our understanding of the features of natural images that guide both human and monkey eye movements. These behavioral studies are at the advanced level of being able to accurately predict patterns of eye movements. The goal of our current investigation is to take advantage of these advancements in predicting patterns of eye movements in natural environments to help us understand the brain events that are responsible for this behavior. I’ll present behavioral results obtained using several new tasks designed to take advantage of models that predict eye position during natural scene search as well as results from multi-electrode array recordings from FEF and surrounding cortex during the performance of these tasks.

Host: Dr. Kording

Tue.  Sept 16

Speaker: Anthony Jarc, PhD

Title: Robotic surgery and sensorimotor control – current research and opportunities

Abstract: Effective surgeon-robot interaction is critical to enhancing the capabilities of surgeons during robot-assisted minimally invasive surgery (RAMIS). Critical to these interactions is a thorough understanding of how a surgeon plans and executes her movements. Conveniently, many aspects of surgeon behavior, such as hand movements and tool trajectories, can be measured unobtrusively during RAMIS. This offers the potential to improve surgeon training, user interfaces, and robot design. Recently, several research groups have applied particular hypotheses and analyses from the fields of human sensorimotor control and motor learning to advance RAMIS. In this talk, I will present an introduction to the da Vinci surgical system, several examples of research that attempts to measure and characterize surgeon behavior, and an overview of academic outreach opportunities supported by Intuitive Surgical, Inc.

Host: Dr. Rymer

Fri, Sept 12

Speaker: Patrick van der Smagt

Title: Machine Learning in Assistive Robotics

Abstract:  The embodiment of assistive and teleoperated devices is one of the central aspects in the application of novel body-machine interfaces. Nonetheless, measuring movement intent remains problematic, as usually only visually apparent movement components are taken into account. But what about impedance, which is a key component when discussing interaction between an actor and its environment?

New machine-learning approaches allow for new measurement methods and improved accuracies with existing interfaces, be they invasive or non-invasive. In this talk I will focus on some methods to the measurement of hand and limb movement and impedance, and the relevance for human-machine interfacing. Applications of our methods on various BMI-based assistive robotic systems will be demonstrated.

Host:  Dr. Mussa-Ivaldi

Fri, Aug 22

Speaker:  Yen-Hsun Wu, PhD

Title:Force Production Coordination among Fingers: Prehension, Pressing, and Effects of Practice

Abstract: Our fingers work together in applying forces and manipulating objects, or sharing loads to accomplish specific tasks. The redundant nature of multi-finger tasks and the ease of measuring all the forces at the fingertip-object interfaces make multi-finger force production a suitable phenomenon for studying motor redundancy. We will look at two multi-finger tasks with apparent redundancy and explore the force coordination among fingers.

The first task required a quick upward movement of a horizontally oriented hand-held object. We explored the force patterns across fingertips, the scaling of those forces with changes in the object properties, and the adjustment of fingertip force vectors during object manipulation. We found that the resultant moment of force was primarily produced by the tangential forces (over 80 %) across all movement phases and loading conditions. The index and little fingers produced close to zero moment with their normal forces, while the normal forces of the middle and ring fingers produced consistent moments due to the reproducible shifts of their centers of pressure.

The resultant force scaled with the external load but not torque, while the grip force scaled with the external torque but not load. The force direction of each digit was kept nearly constant in the object-centered referent frame across the loading conditions and movement phases.
The second task explored the effects of practice on the multi-finger synergies during accurate pressing force production. Multi-finger synergies stabilizing the sum of involved finger forces (FTOT) were quantified within the uncontrolled manifold (UCM) hypothesis framework. Total amount of variance (VTOT) in the space of finger forces across repetitions were decomposed into two components, VUCM that had no effect on and VORT that affected FTOT. Indices of synergies were computed as the difference between VUCM and VORT normalized by VTOT. Tasks with graded instability composed a special practice schedule to encourage using variable patterns of finger involvement that are equally able to produce accurate FTOT. We found that variability of FTOT decreased and performance became more accurate after the practice. In contrast, variance in the space of finger forces increased. These effects were retained for two weeks. Transfer of these effects to different tasks was not consistent suggesting high specificity of coordination changes.

Overall, the results in these two multi-finger tasks suggest two features of finger force production. First, the central nervous system might facilitate a simple scaling rule to adjust fingertip forces. Second, the coordination among fingers is adaptable to practice of tasks designed to encourage use of variable elements. We view the results as promising for future use in populations with impaired coordination characterized by low synergy indices, such as patients with Parkinson’s disease. The protocol with adjustments in task instability can also be used to train a wide range of motor tasks, such as reaching movement, postural tasks, and locomotion.

Host: Dr. Rymer

Fri, Aug 15

Speaker:  Babak Afsharipour, PhD

Title: High Density sEMG (HDsEMG) Recording: Features, Cautions, and Applications

Abstract: The technique, based on NxM electrode grid is referred to High-density sEMG (HDsEMG) or EMG imaging. In HDsEMG recording, each electrode may be conceived as a pixel “p” with coordinates (x,y) given by the rows and columns in the grid. Muscle activity can be considered as a movie whose frames are generated by the samples of the amplitude (instantaneous, average rectified value, or root mean square) of each channel. In such maps, the resolution, which is defined by the inter-electrode distance (IED), is important. To avoid spatial aliasing in sEMG maps, electrode girds with the IED<10 mm are recommended.
Electrode grids provide a spatial distribution (a map) of muscle electrical activity. Specific regions within these maps are of interest. Image segmentation is a technique for partitioning an image (data set) into regions of interest and is used in many different fields. Different methods are available and three methods have been applied for the automatic segmentation of EMG images by researchers. It is found that watershed segmentation is preferable to the K-means and h-dome segmentations as watershed provides higher accuracy value and it is more robust to the signal to noise ratio, fat thickness and threshold levels.

HDsEMG technique has been applied to study musicians. Musicians, Industrial workers and populations whose job requires daily intensive repetitive tasks may suffer from musculoskeletal disorders after some years. Musicians are a large human population who may start their work and their training from early ages. Becoming a professional player can be considered as a goal which motivates this population to work as hard as possible in a repetitive task that leads to playing-related musculoskeletal disorders (PRMDs) on muscle activity with a prevalence of up to 80%. sEMG activity distribution on upper and lower trapezius muscles of the bowing arm, left & right erector spinae muscles were recorded during playing (a-large bowing, b-small but fast bowing) standard notes. Presence of a back rest during playing was also studied. This study is still in progress. Preliminary results show that all recorded muscles (trapezius and erector spinae muscles) were activated to a different extent and the muscles activation significantly (p<0.05) depend on the string that was played.

Host:  Dr. Rymer

Fri, Aug 8

Speakers: Administrative and Technical Representatives from the NU Clinical and Translational Sciences Institute (NUCATS)

Title:  eNOTIS Training Session for RIC Researchers

Abstract: This is an informational session on the July 16th email below about the FSM Clinical Research Participant Tracking Policy, and a Training Session on the use of the eNOTIS system. This pertains to all RIC researchers. Please read the attached policy and bring your specific questions for discussion.

The following learning objectives/questions will be directly addressed for RIC Researchers:

  1. What is the eNOTIS system and what is its purpose?
  2. Who has access to eNOTIS/How can I get access to eNOTIS?
  3. When do I have to begin using eNOTIS? 
  4. What is the minimum information that I need to collect from my subjects in order to enter them into eNOTIS?
  5. How do I complete data entry of a subject into eNOTIS? A step-by-step demonstration will be given on how to use the eNOTIS system.
  6. Who can I contact if I need more help?

Host: Dr. Rymer

Fri, Aug 1

Speaker:  Tom Ferrone

Title:  Patents at RIC

Abstract: Tom will discuss the basics of the patent process at RIC, including the elements of a patent, considerations for inventors working in a research setting, and RIC’s process for filing a patent application. Please join us if you have wondered whether your research is patentable, if you want to know how to disclose your research while making sure it stays patentable, or if you would like to learn more about the patent process at RIC.

Host:  Dr. Kuiken

Wed, July 30

Speaker: Derek Miller

Title:  Vestibular Pathway Contributions to Post-Stroke Spastic Hypertonia

Abstract: Spasticity after stroke is a frequent and often disabling sequel of the vascular incident, manifesting as an increase in the resistance of a passive limb to externally applied joint rotation. It occurs following lesions that appear to disrupt cortical modulation of brainstem nuclei, which regulate motoneuron excitability. Although quite prevalent, the etiology remains uncertain. Indirect evidence suggests that the lateralized changes in motoneuron behavior post-stroke are due to a low-level depolarizing supraspinal drive, but the pathways responsible are unknown. It has been proposed that altered vestibular function, mediated by vestibulospinal projections, could account for post-stroke spasticity. Therefore, the purpose of this study was to examine the hypothesis that the increased reflex responses and hypertonia seen in spastic-paretic muscles following a hemispheric stroke are due to spinal motoneurons being held abnormally close to their threshold for activation by input from descending vestibulospinal pathways. In the first part of the thesis, we recorded cervical vestibular evoked myogenic potentials in the neck muscles of spastic hemiparetic stroke subjects, to quantify the relative levels of sacculocollic drive to the spastic-paretic and contralateral sternocleidomastoid motoneuron pools. In the second part, we elicited sound evoked biceps myogenic potentials in spastic hemiparetic stroke subjects to assess the relative levels of vestibulospinal drive to the spastic-paretic and contralateral biceps motoneuron pools. In the third part, we examined ascending otolith-ocular projections. In all three studies, side-to-side differences in reflex amplitude will be expressed as an asymmetry ratio, a proxy for the relative amount of vestibular drive to the affected and spared motoneuron pools. We also examined the relationship between response asymmetry and the severity of spasticity. After stroke, vestibular drive to cervical and ocular motoneuron pools is asymmetrically distributed, supporting our hypothesis that there is an imbalance in descending vestibular drive to motoneuron pools secondary to stroke. Additionally, we found that in a subpopulation of subjects, there was a relationship between the degree of reflex asymmetry and limb muscle spasticity. We speculate this imbalance is a consequence of the disruption of inhibitory corticobulbar projections to the vestibular nuclei. This study sheds new light on the underlying mechanisms of spasticity following stroke.

Host:  Dr. Rymer

Fri, July 25

Speaker: Suzann K. Campbell, PT, PhD, FAPTA

Title: Effects on Motor Performance of Kicking and Stepping Exercise in Infants with  Periventricular Brain Injury: A Pilot Study

Abstract:  Infants with perinatal periventricular brain injury (PBI) have a high incidence of atypical development and atypical leg movements. The purpose of this study was to determine whether a home-based kicking and treadmill stepping intervention program beginning at 2 months corrected age (CA) in children with PBI improves motor function, walking, and brain development at 12 months CA when compared with control subjects.  Sixteen infants with PBI were randomly assigned to exercise (kicking and treadmill stepping) or a no-training control condition. Development was assessed at 2, 4, 6, 10, and 12 months CA with the Alberta Infant Motor Scale (AIMS) and at 4 months with the Test of Infant Motor Performance (TIMP). At 12 months children were classified as normal, delayed, or with cerebral palsy (CP).

At 12 months CA half of the subjects had CP or delayed development on the AIMS, but no significant differences between groups in AIMS scores were found at any age.  Three of 7 (43%) of the exercise group children walked alone or with one hand held versus 1 of 9 (11%) in the control group (p=.262).  Brain maturation as measured with DTI at 12 months CA was correlated with developmental outcome on the AIMS at .82.  A behavioral analysis of kicking behavior in the mobile paradigm showed that most children increased their kicking frequency between 2 and 4 months of age and appeared to attend to and enjoy the activity, suggesting feasibility of the intervention, but parent compliance with the home program was inconsistent, suggesting that the dosage of the intended intervention was deficient for meeting the goals of the study.  Kicking frequency at 4 months CA was significantly correlated with development on the TIMP at .54.  Although not statistically significant with a small sample size, results suggest a possible effect on age at walking of self-produced kicking and treadmill exercise, but improvements of the protocol to increase compliance are needed.

Host:  Dr.  Jayaraman

Fri, July 18

Speaker: Jordan Taylor, PhD

Title: Multiple paths to success in visuomotor learning

Abstract: Traditionally, visuomotor learning has been regarded as reflecting a unitary function involving implicit “procedural learning”. More recently, however, it is becoming clear that multiple learning processes can be involved. In the case of a visuomotor rotation, which is a visual mismatch between movement and feedback, the motor system needs to counter the rotation by moving in a direction opposite to the rotation. This solution can potentially arise through a number of different learning processes, such as internal model adaptation, reinforcement learning, and strategy utilization. The relative contribution of each process may be influenced by various factors including the type of feedback used to indicate action outcomes, the form of the instructions that shape how the task is conceptualized, and manipulations of visual cues in the environment. The aim of the current set of studies is to unravel how these factors influence learning a visuomotor rotation.

To elucidate these different learning processes we manipulated information in error feedback, verbal instructions, and visual landmarks in the task workspace while participants learned to counter a visuomotor rotation. These manipulations had a profound effect on how the rotation was countered. With reduced error feedback, the learning curves exhibited a high degree of variability until the correct aiming location was discovered, and then stabilized. This form of learning is reminiscent of reinforcement learning tasks where learning occurs through exploratory trial-and-error until an action is reinforced. In contrast, with more informative error feedback, performances curve were monotonic with a smooth reduction in target error during training. Aftereffects, a measure of the degree of sensorimotor remapping, scaled as a function of the information in error feedback suggesting that detailed cursor information is necessary for training an internal model. Increasing information in instruction also increased trial-and-error learning through exploration of the action-outcome space. Finally, the visual landmarks provided an anchor for developing explicit strategies to counter the rotation and also provided a means to directly assay the contribution of explicit learning during training. We find that participants utilized various strategies throughout training and that the degree of their engagement appears to be the result in a push-pull interaction, with reward-based learning potentially suppressing error-based adaptation. Taken together, these results suggest that a rotation can be solved by multiple, different learning systems and differences in information in feedback, instruction, and visual cues may bias the relative contribution of different learning processes.

Host:  Dr. Kording

Fri,  July 11

Speaker:  Iris Vilares

Title: Uncertainty and Decision Making in the human brain

Abstract:    Uncertainty pervades most of the events and decisions that we face every day. Uncertainty exists in previously acquired knowledge (prior) and on what our senses currently tell us (likelihood). Moreover, uncertainty exists in both non-social and social settings (social uncertainty). Understanding how the brain responds to and uses information about uncertainty thus seems crucial if we want to understand decision-making. Here, we developed a decision-making task in which both prior and likelihood uncertainty were varied and had subjects perform the task while we scanned their brains using functional magnetic resonance imaging (fMRI). We found that the brain represented both types of uncertainty, but they had very distinct representations: likelihood uncertainty activated brain areas along the early stages of the visuomotor pathway, while prior uncertainty was associated with increased activations in specialized brain areas outside this pathway, namely putamen, amygdala, insula and orbitofrontal cortex. Furthermore, activity from the putamen also correlated with subjects’ tendencies to sense and attend to current versus prior information. Our results thus suggest different pathways through which prior and likelihood uncertainty are represented in the human brain, offering insights into the neural pathways that allow humans to make decisions.

Based on the obtained results, we next aimed to understand the specific role putamen activity had in decision-making under uncertainty. Furthermore, because dopamine is one of the main neurotransmitters of the putamen and has previously been implicated in decision-making under uncertainty, we also sought to understand the influence dopamine plays in the decision-making process. For that purpose we recruited patients with Parkinson’s disease (PD), in whom the putamen activity is compromised due to a lack of dopamine, to perform the same task, and compared them with age-matched controls. We hypothesized that if dopaminergic activity from the putamen is causally involved in some aspect of decision-making under uncertainty, this will then show in the way PD patients perform the task. Moreover, we hypothesized that these differences would be particularly salient if PD patients performed the task after they were off dopaminergic replacement medication overnight (off-state), compared with if they just took their medication 1 hour before (on-state). We found that some aspects of decision-making under uncertainty were conserved in PD patients: both groups could learn prior distributions and use prior and likelihood information. However, PD patients, particularly in the off-state, were impaired at reacting to differences in likelihood uncertainty. Together, our results indicate that dopaminergic activity from the putamen has a crucial role in the processing of uncertainty in the current sensory stimulus (likelihood uncertainty), potentially through increased attention towards it.

Host: Dr.  Kording

Tues, July 1

Speaker: Raymond Tong, PhD

Title: Effects of Different Rehabilitation Exercises using a Stroke Rat Model

Abstract: Stroke remains one of the major causes of mortality and long term disability throughout the world. Exercise paradigms have been effective rehabilitation tools in facilitating motor function recovery after strokes. Challenges in stroke rehabilitation with exercise interventions include the time window for training, the selection of different types of exercise and the mechanisms of exercise-induced recovery. Clinical practices suggest that the rehabilitation exercise should not be administered to patients until their cerebrovascular flow, which is difficult to monitored, has reached to a steady state. In addition, the effects of difference exercise paradigms are still largely unexplored and not systematically compared. In our research team, the cerebrovascular changes during strokes are investigated; the effectiveness of the voluntary, involuntary, and forced exercises are compared; and the possible mechanisms of the exercise-induced recovery are proposed.

The effectiveness of these exercises in facilitating motor recovery and up-regulating brain neurotrophic factor (BDNF) after brain ischemia has not been systematically compared. We designed four groups: Control (Con), Voluntary exercise of wheel running (V-Ex), Forced exercise of treadmill running (F-Ex), and Involuntary exercise of FES (I-Ex) with implanted electrodes placed in two hind limb muscles on the affected side to mimic gait-like walking pattern during stimulation. Ischemic stroke was induced in all group rats with the middle cerebral artery occlusion/reperfusion model. The results showed that the V-Ex group had significantly better motor recovery in the behavioral test and significantly higher hippocampal BDNF concentration than the F-Ex and Con groups. On the other hand, the F-Ex group had significantly higher serum corticosterone level than the other groups. These results suggested that the voluntary exercise was the most effective intervention in upregulating the hippocampal BDNF level, and facilitating motor recovery. Rats that exercised voluntarily also showed less corticosterone stress response than the other groups. The results also suggested that the forced exercise group was the least preferred intervention with high stress, low brain BDNF levels and less motor recovery.

Host: Dr. Kamper

Fri, June 20

Speakers: Carrie Peterson, PhD and Marije deBruin, PhD


Title: A comparison of two surgical procedures that enable active elbow extension after spinal cord injury

Abstract: Individuals who sustain a spinal cord injury at the C6 level or higher lack active elbow extension, which severely limits their independence. Two surgical procedures can enable active elbow extension after C5 and C6 level injuries via reassignment of a non-paralyzed muscle (either the biceps or posterior deltoid) to the tendon of the paralyzed triceps muscle. We compared the efficacy of these tendon transfer procedures with regard to an individual’s ability to activate the transferred muscle, and the amount of elbow extension strength restored in three functional arm postures. Our data suggest the biceps-to-triceps procedure results in greater elbow extensor strength. Deficits in voluntary activation were more prevalent after posterior deltoid-to-triceps transfer and further decreased elbow extensor moments relative to the biceps-to-triceps transfer. Additionally, we assessed corticomotor excitability of the transferred biceps using transcranial magnetic stimulation. Corticomotor excitability of the transferred biceps was positively related to elbow extension strength suggesting therapies that purposefully increase excitability may be beneficial.


Title: Methods to Record Maximum Muscle Activity from the Extrinsic Thumb Muscles

Abstract: In general, there is not an accepted, standardized protocol for measuring maximum voluntary contraction (MVC) of the extrinsic thumb muscles. This is problematic because normalization of measured electromyographic (EMG) signals to MVC allows for between-day, between individual, and between-muscle comparisons of activation levels. Standardization of positioning for MVC testing has been shown to be difficult for individual shoulder muscles, which like the thumb, is a system of joints with high mobility. We aim to objectify a standard set of positions for MVC testing for the four extrinsic thumb muscles.

Host: Dr. Murray

Fri, June 13

Speaker: Andy Kondrat

Title: The Ethics of Incidental Findings: Research, Reactions and Recommendations

Abstract: Recently, the Presidential Commission for the Study of Bioethical Issues released Anticipate and Communicate, a report detailing the ethical management of incidental findings in a variety of medical contexts, including the research setting. The Commission discusses researchers’ responsibilities for discovering and disclosing incidental findings with regard to the values of respect for persons, beneficence, justice, and intellectual freedom.

In this interactive session, we will examine the recommendations of the Presidential Commission in the context of research being performed at RIC. Our local philosopher, Andy Kondrat, bioethicist in the Donnelley Ethics Program will give a brief overview of the report and the issues contained within and then we will open it up for a lively discussion. Please come with your thoughts or examples of incidental findings. The session is open to all RIC employees and affiliates.

Fri, May 30

Speaker: Suzanne Sokalski, Research Education Specialist, NU IRB Office

Title: Informed Consent

Abstract:  This talk will consist of a discussion of the Federal regulations and NU/RIC policy requirements for obtaining and documenting informed consent from research participants.
The following learning objectives will be directly addressed:

  1. Define the scope of the research Informed Consent process
  2. Learn how to properly document research Informed Consent
  3. Review the elements of the Informed Consent document and discussion with the research subject
  4. Review and discussion of a few case studies
  5. Discuss success tips and tools

Tues, May 27

Speaker: Dr. Pablo Gagliardo

Title: NeuroAtHome: applying natural interfaces and gamification to motor and cognitive rehabilitation

Host: Eric Larson

Thurs, May 22

Speaker: Eric Shearer

Title: Efficient Identification of Multiple-Muscle Functional Electrical Stimulation Systems

Abstract:  This thesis develops a method to identify the dynamics of a human arm controlled by functional electrical stimulation and use a model of the arm to control force and motion of the hand. Functional electrical stimulation is a means to restore basic daily functions that require reaching to people with high spinal cord injuries. The previous state of the art of FES control does not provide the flexility to achieve arbitrary tasks routinely performed by people who do not have spinal cord injuries. The model developed in this thesis accounts for coupling of joints of the arm as well as the kinematic and muscular redundancy that make the human musculoskeletal system flexible to different tasks. The model allows the use of centralized control strategies which are well-studied in robotics.

The model identification technique involves stimulating muscles at different configurations of the arm while measuring the joint configuration and velocity along with interaction forces at the hand. A model for static force output at a subject’s arm was identified and used for control. Over a large space of 3D endpoint forces the controller could predict a force at the hand produced by stimulation of the muscles within 11% of the maximum force produced by muscle stimulation. A model for the shoulder and elbow torques produced by muscles while the hand moves along smooth reaching trajectories was identified and used for control. The model’s predictions of shoulder and elbow torques was an average less than 20% of the maximum torque produced by muscle stimulation. The model was used for a demonstration of motion control of the hand. The muscle stimulations decreased the amount of torque required to move the hand.

Finally, the model’s ability to predict torque for new areas of the model’s input space was assessed. A purely black box model will not make accurate torque predictions when presented with inputs unlike those used for training the model. A semiparametric model that incorporates knowledge of the arm dynamics into a Gaussian process model has much smaller expected errors in shoulder and elbow torque predictions than the purely black box model for inputs unlike those used for training the model.

Advisor: Dr. Lynch

Tue, May 20

Speaker: Eva Dyer

Title: Low-dimensional signal models for large-scale machine learning

Abstract:  The abundance of cheap storage and sensing devices has led to a deluge of high-dimensional data. However, while the dimensionality of modern datasets continues to grow at an unprecedented rate, these data often exhibit low-dimensional structure that can be exploited to organize, cluster, or decompose the data. In this talk, I will describe how union of subspace models, which model data as living on a mixture of subspaces, provide a powerful generalization to single subspace and manifold models and can be used to more effectively capture the structure present in large datasets. Finally, I will describe our recent efforts towards developing new methods and theory for learning unions of subspaces and exploiting low-dimensional structure in big data.

Host: Dr. Kording

Fri, May 2

Speaker: Randolph J. Nudo, PhD

Title: Neuroprosthetic tools for repair of the injured brain

Abstract: Neuroprosthetic devices generally can be categorized as open-loop neuromodulation systems, that directly or indirectly excite neural tissue, or brain-computer interfaces, that derive control signals from the brain to operate external devices. Increasingly, neuroscientists, computer scientists and engineers are beginning to envision and develop closed-loop systems that stimulate neuronal populations contingent upon a particular neuronal signal derived from another population of neurons. In the near future, investigations into the feasibility and efficacy of closed-loop systems for treating neurological conditions will likely emerge. Such conditions will include epilepsy, Parkinson’s disease, and potentially stroke, traumatic brain injury and spinal cord injury. Thus, it is now critical to understand how such systems interact with the neural circuitry and how communication may be altered. Our current research program focuses on the potential ability for closed-loop systems to regulate synaptic potentiation in long-distance pathways in the nervous system, particularly cortico-cortical pathways between different functional areas. Because the demonstration of long-term potentiation and long-term depression in animal preparations has utilized stimulation timing protocols that are not typically feasible using non-invasive techniques, our current pre-clinical model employs recording microelectrodes implanted within the cerebral cortex, and microdevices that discriminate individual action potentials, process discriminated spikes from multiple input channels, and then electrically stimulate remote brain regions using implanted microelectrodes. Recent studies have demonstrated the ability of this closed-loop system to modulate synaptic potentiation between the two areas and promote functional recovery after brain injury. Despite the challenges of invasive procedures using implantable technology, such closed-loop systems have the potential to provide new treatment avenues in a host of neurological conditions.

Host: Dr. Miller

Mon, April 28

Speaker: Michael Wagner

Title: Building Safer Robots

Abstract: Robots have the potential to reduce accident rates and boost efficiency in a range of applications. However the risks posed by technologies used in autonomous robots are sometimes poorly understood and inaccurately modeled. Some may chalk this up to simply the novelty of cutting-edge technologies, but I believe that traditional methods of mitigating risk cannot be applied easily to systems where a machine, rather than a person, is in control.
This talk is a broad introduction to the challenges that we face when building reliable and safe autonomous robots. The talk explains why the models of the world central to autonomous systems can be difficult to test, or even analyze, for hazards. In response, I discuss potentially helpful findings from research aimed at building structured safety cases, mitigating risks architecturally, and stress-testing complex software.

Host: Dr. Argall

Fri, April 25

Speaker: Song Joo Lee, PhD

Title: Effects of Six-Week Pivoting Neuromuscular Training on Offaxis Neuromechanical Properties in Males and Females

Abstract: Musculoskeletal injuries of lower limbs often occur in pivoting sports and females are at higher rate of injuries than males. However, there is a lack of information on gender differences in offaxis neuromechanical properties in axial plane pivoting and frontal plane sliding and methods to improve offaxis neuromuscular control under injury related situations. The goal of the research was to investigate effects of genders and 6 week neuromuscular training on lower limb offaxis neuromechanical properties.

First, gender differences of proprioception and neuromuscular control in pivoting under external perturbations, and offaxis neuromuscular control under slippery conditions were investigated. Compared to males, females demonstrated lower proprioceptive acuity under weight-bearing and decreased pivoting neuromuscular control with higher pivoting instability, lower leg pivoting stiffness, and entropy of time to peak EMG in gastrocnemius muscles during stepping under external perturbations and decreased offaxis neuromuscular control during stepping under slippery conditions.

Second, effects of 6-week pivoting neuromuscular training on proprioception and neuromuscular control under external perturbations and slippery conditions were investigated. Six-week pivoting neuromuscular training improved proprioceptive acuity and neuromuscular control under injury-related situations, and females benefited more from the training.
The secondary goal of the research was to investigate effects of 3D knee geometries and gender dependent tibial external rotation laxity on the susceptibility of ACL impingement against the femoral intercondylar notch using a finite element knee model.Our findings suggest that 3D knee geometries and joint laxity alter biomechanical contact properties between the ACL and femur.

Overall, the research investigated effects of gender differences and 6-week neuromuscular training to understand potential modifiable and non-modifiable risk factors of musculoskeletal injuries, ACL injuries in particular. This study may help understand factors contributing to musculoskeletal injuries in females and males, and develop neuromuscular training strategies to improve neuromuscular control and proprioceptive acuity.

Host: Dr. Zhang

Fri, April 18

Speakers: Lois Huggins and Kathy Galvin

Title: Communicating With Influence

Abstract:   Communicating With Influence highlights effective communication skills, including Active Listening and Assertion, to enhance participants’ communication and interpersonal skills, and to increase participants’ ability and confidence to provide feedback to others.  It is an interactive one-hour session.

Host: Dr. Kuiken

Wed, April 16

Speaker: James Buffi

Title: Using Biomechanical Simulation and Modeling to Calculate Potential Muscle Contributions to Elbow Varus Torque during Baseball Pitching

Abstract: Failures of the ulnar collateral ligament (UCL) and damage to the osseous articulation of the elbow are common and severe elbow injuries that occur in baseball pitchers as a result of the excessive elbow valgus torque imposed by the baseball pitching motion. Despite high injury risk to elbow musculoskeletal structures during pitching, research characterizing muscle contributions to protecting this joint during the pitching task is extremely limited. One reason for this limitation is that common experimental methods in cadavers and living subjects are not sufficient to understand muscle function in this high-performance, high-velocity, multiarticular task. Consequently, biomechanical modeling and simulation are required to better understand individual muscle contributions and associated injury implications. The goals of this project were to develop a simulation framework for the baseball pitching motion and to use this framework to characterize potential muscle contributions to protecting the elbow joint during this complex task.

To achieve these goals, an upper-extremity and a whole-body musculoskeletal model were developed for use in a quasi-static sensitivity analysis and a forward dynamic analysis, respectively. Additionally, because an important medial elbow muscle (flexor digitorum superficialis) inserts in the hand, a method was defined and evaluated for recording hand motion with an instrumented glove. The quasi-static simulation indicated that adopting a flexed elbow posture at a critical time point in the pitching motion substantially decreased the ability of the medial elbow muscles to generate protective varus torque. Therefore, a more extended elbow posture may mitigate elbow injury risk. In a forward dynamics simulation of a single subject’s pitching motion, activation and contraction dynamics limited the ability of the medial elbow muscles to actively counter the rapid increase in elbow valgus torque imposed by the pitch. In simulation, it was demonstrated that the intrinsic stiffness properties of muscles that allow them to instantaneously respond to perturbations may be an essential mechanism necessary to protect baseball pitchers from UCL injury. Overall, the simulation framework developed in this project represents an essential advancement to the field of pitching biomechanics that, for the first time, allows researchers and clinicians to evaluate potential contributions of the elbow muscles.

Host: Dr. Murray

Wed, April 9

Speaker: Yunju Lee

Title: On the Behavior of the Adult Upper Extremity under Impulsive End-Loads?

Abstract: Falls in the elderly are a serious socioeconomic problem for which costs have reached $30 billion/year in direct costs alone. The reality of aging is that one loses about 1% of muscle strength/year after the age of 55 years. When this loss of muscle strength is combined with obesity, the strength-to-weight ratio becomes unfavorable and the upper extremity muscles may no longer be able to prevent the arms from buckling at the elbows in a fall. The result can be head injury and even death.

In this seminar we shall review a novel apparatus and the experimental methods we used to identify the viscoelastic properties of active upper extremity muscles in healthy young and older adults identified via dynamic optimization techniques. We shall discuss in silico studies that employed ADAMS multi-body dynamics computer models to show that older females have a 25% lower arm buckling load than young females of the same body size. We will also examine the question of whether the muscle reflexes are fast enough to stiffen the arm protraction muscles during a fall arrest. Finally we discuss the utility of this research in providing exercise or rehabilitation goals for the upper extremities of older adults.

Host: Dr. Zhang

Tues, April 8

Speaker: Nathalia Headley, David Wingate, and David Zembower

Title: Conducting Investigational Drug Studies

Abstract: This presentation will focus on accomplishing the following learning objectives:

  • Debriefing on the Q2 FY2014 Corporate Compliance Investigational Drug Study Audit
  • Identify the key requirements in the FDA and IRB regulations, and RIC policies
  • Identify what your primary roles and responsibilities are in conducting investigational drug studies
  • Discuss helpful tips and pointers to run your drug study effectively and protect human subjects
  • Identify your primary references and resources, and know where to go and who to contact for additional help

Fri, April 4

Speaker: Christian Ethier, PhD

Title: Brain-controlled muscle stimulation: a neuroprosthesis for the restoration of grasp function after paralysis

Abstract: We have developed a neuroprosthesis that allows monkey subjects to pick up and move objects despite a peripheral nerve block causing complete paralysis of the flexor muscles below the elbow. The restored voluntary movement was achieved using signals recorded from approximately 100 neurons in the primary motor cortex to control electrical stimulation of the paralyzed muscles. After nerve block, the monkeys were able to use the neuroprosthesis to perform a functional grasping task with a success rate approaching their normal performance, whereas they were essentially unable to complete this task without assistance. We are now investigating adaptive decoders to facilitate the implementation and improve the performance of this neuroprosthetic system in chronically paralyzed subjects. In human spinal cord injured patients, such a system could provide natural control of arm and hand movements through normal cognitive processes, and greatly enhance the patients' independence and overall well-being.

Host: Dr. Miller

Fri, March 21

Speaker: Suzanne Sokalski

Title: IRB 101

Abstract: Please join us for a discussion of:

  • When does the IRB need to be involved?
  • What kind of review is appropriate for your project?
  • What are IRB reviewers looking for?
  • Practical tips for submitting in eIRB
  • Your questions

Fri, March 14

Speakers: Paul Wanda, PhD and Matt Perich

Title and abstract (Paul): Signatures of uncertainty in motor and dorsal premotor cortex of non-human primates

Behavioral studies show that humans can combine noisy information from previous experience and current feedback to guide their movements in a near Bayes-optimal manner. However, little is known about the neural encoding of uncertainty. Here, we designed a behavioral paradigm to test several theoretical models with electrophysiological data. We trained macaques to perform a modified center-out reaching task and found evidence of Bayes-like weighting of sensory feedback in the monkeys’ behavior. We recorded neural signals from macaque dorsal premotor cortex (PMd) and primary motor cortex (M1) using chronically-implanted, 96-channel multi-electrode arrays. As feedback uncertainty increased, we found that both firing rates and across-trial rate variability increased across the population of recorded PMd neurons, initiating during planning (non-movement) phases. These results suggest a complex neural code for uncertainty in motor areas.

Title and abstract (Matt): Neural correlates of adaptation to dynamic and kinematic perturbations in motor cortex

Coordination of visually guided movements requires a transformation from planned kinematics to executed dynamics that must be learned through trial and error and the adaptation of an internal model. Thus motor adaptation may be mediated by adjusting the computations performed by M1 and PMd. The differing functional roles of M1 and PMd in coordinating movement suggest different roles in motor adaptation. To test this, we compared neural activity during adaptation to two reaching perturbations: a static visual rotation (VR) or viscous curl force field (CF). The CF affected only the dynamics of the movement, and when fully adapted, the kinematic trajectories were identical to the unperturbed reaches. In contrast, the VR required new planned trajectories to reach the targets. We described the spatial tuning of each recorded neuron using a preferred direction (PD). We found that when correlating activity with the actual direction of hand movement, M1 PDs were constant during adaptation to both perturbations even as task performance improved. PMd neurons, in contrast, showed an apparent change in tuning with the same analysis methods. However, PMd tuning was stable during adaptation if the tuning was instead calculated with respect to the target direction. These results highlight the functional differences between PMd and M1 in coordinating limb movements, where M1 activity relates to the dynamics of the movement and PMd relates primarily to the goal.

Host: Dr. Miller

Fri, March 7

Speaker: Ghulam Rasool

Title: Task-specific Muscle Synergies – A Novel Framework for Task Discrimination

Abstract: The control of an artificial robotic limb using myoelectric signals from leftover muscles in amputees is a challenging problem in rehabilitation engineering. We present a novel scheme to tackle the problem by employing task-specific muscle synergies and state-space representation of the neural signals. The proposed framework incorporates information about muscle configurations, e.g., muscles acting in agonist /antagonist pairs or synergistically, using the hypothesis of muscle synergies. The neural drive, comprised of muscle synergy activation coefficients, is modeled as the unknown latent system state. Subsequently, we employ a recursive Bayesian technique to estimate the neural drive. The estimated neural drive is later used to discriminate between various tasks. The task discrimination decisions by the proposed scheme are further improved by a post-processing routine using posterior probabilities. The proposed algorithm is robust and computationally efficient yielding a discrimination decision in approximately 3 ms. Real-time performance and controllability of the algorithm was evaluated using the targeted achievement control (TAC) test. Based on the results of this study, the proposed algorithm outperformed the commonly employed linear discriminant analysis (LDA) algorithm in off-line accuracy (p<.001) and real-time performance (p<.01) for single as well as multi-degree-of-freedom (DOF) tasks.

Host: Dr. Rymer 

Thurs, March 6

Speaker: Jeremy Newkirk, PhD

Title: Measurement and Quantification of the Human Shoulder Girdle Motion and Design of a Humanoid Shoulder Girdle Mechanism with Minimal Actuation

The shoulder girdle plays an important role in the large pointing workspace that humans enjoy. The goal of this work was to characterize the human shoulder girdle motion in relation to the arm and recreate it with a humanoid shoulder girdle mechanism so as to ultimately improve the human-like motion of humanoids. The overall motion of the human shoulder girdle was characterized based on motion studies completed on test subjects during voluntary (natural/unforced) motion. The collected data from the experiments were used to develop surface fit equations that represent the position and orientation of the glenohumeral joint for a given humeral pointing direction. These equations completely quantify gross human shoulder motion relative to the humerus. The equations are presented along with goodness-of-fit results that indicate the equations well approximate the motion of the human glenohumeral joint. This is the first time the motion has been quantified for the entire workspace, and the equations provide a reference against which to compare the motion of candidate humanoid shoulder girdle mechanisms. A novel 2-degree-of-freedom parallel mechanism composed of two platforms, one leg with two revolute joints and two legs with spherical-prismatic-spherical joint combinations (1-RR, 2-SPS), is introduced and analyzed. The results from the data collection were used to find the optimal configuration for this mechanism to mimic human shoulder girdle motion. The results indicate that the optimized mechanism well approximates the motion of the human shoulder girdle, making it the first mechanism that replicates human shoulder girdle motion with minimal actuation. The methodology for incorporating the shoulder girdle mechanism into the shoulder-elbow complex is presented. The kinematic equations of motion for the complex were derived, and a qualitative analysis was completed that indicates the motion of the full system is similar to that of the human shoulder-elbow complex. The work presented here lays the groundwork for replicating complex human shoulder girdle motion with a relatively simple robotic system. 

Host: Dr. Kuiken

Tue, March 4

Speaker: Ross Arena, PT, PhD

Title: CPX: Reinventing Clinical and Research Applications

Abstract: Cardiopulmonary exercise testing (CPX) is clinically indicated for several diagnoses/suspected diagnoses with a wealth of scientific evidence supporting its value.  Moreover, the use of CPX as a primary or secondary research endpoint, when an exertional assessment is needed, is readily justifiable.  The appropriate application of CPX for clinical or research purposes has been somewhat hindered by the high volume of data generated and a lack of clarity on which variables are most relevant for a given test indication.  This presentation is based on the recent EACPR/AHA joint statement that significantly consolidates CPX interpretation based upon test indication and current evidence. 

Host: Dr. Rymer 

Fri, Feb 28

Speaker: Reza Shadmehr, PhD

Title: A memory of errors in sensorimotor learning

Abstract: When performing a motor task, experiencing an error results in a change in motor behavior on the next trial. Models of this behavior typically feature one or more fixed error-sensitivity parameters that describe the percentage of the error that is accounted for in the next trial. However, these models of learning cannot explain recent motor control results in areas such as savings, meta-learning, and saturation in the amount that is learned from a sensory prediction error. Here we show that the brain modulates, through a principled mechanism, how much it is willing to learn from error. To understand the rules that govern changes in error-sensitivity, we perform experiments which manipulate the statistics of the perturbations, altering the history of experienced errors, and record its effects on error-sensitivity. We find that positive lag-one autocorrelations up-regulate error-sensitivity local to the specific errors that were experienced, whereas negative autocorrelations down-regulate error-sensitivity. Our results suggest that motor memory is composed of both a memory of actions and a memory of previously experienced errors. This memory of errors sheds new light on a number of puzzling observations, including savings and meta-learning.

Host: Dr. Miller 

Fri, Feb 21

Speaker: Yasin Seven, PhD

Title: Neuromotor Control of the Diaphragm Muscle: Functional Recovery after Cervical Spinal Cord Injury

Abstract:  Diaphragm muscle (DIAm) is activated during ventilatory and non-ventilatory motor behaviors, which require different levels and patterns of central drive as well as involve different central pattern generators. DIAm motor units are diverse in their mechanical and fatigue properties. Therefore, how these motor units are being recruited determines the force and fatigability of muscle contractions. DIAm single motor unit activity was assessed in rodents exhibiting spontaneous recovery after spinal cord injury across resting breathing, hypoxia-hypercapnia, sighs and airway occlusion.

Due to limitations of single motor unit recordings, compound EMG was simultaneously recorded to measure DIAm activity. So far, it is unclear how much information can be obtained about motor unit activity using compound EMG. DIAm EMG power spectral density shifted to higher frequencies with the recruitment of fatigable fast-twitch motor units during sneezing (maximal DIAm force). Additionally, the non-stationary period of DIAm EMG reflected the time period where DIAm motor units are being recruited.

Host: Dr. Rymer

Tue, Feb 18

Speaker: Robert Ajemian, PhD

Title: The Perpetual Motion of Motor Memories and How they Differ Profoundly from Computer Bytes

Abstract: From throwing a baseball to playing the piano to using the latest I-Phone keypad, humans are constantly acquiring novel sensorimotor skills throughout the course of their lives.  A fundamental goal of neuroscience has been and continues to be an elucidation of neuroplasticity – that is, the neural mechanisms underlying motor memory acquisition and storage.  For over a half-century, the computer metaphor has shaped the neuroscience community’s thinking regarding the transfer and storage of information.  According to this viewpoint, the nervous system lays down a synaptic trace during learning, and, while the details of this process are quite complex (LTP, LTD, spike-timing dependent plasticity, etc.), the interpretation of the memory is unambiguous.  The memory IS the desired synaptic trace.  Further, as long as this trace remains intact, so too does the memory.  However, there are clear functional and architectural differences between the inorganic circuitry of a computer chip and the biochemical environment of a neuron.  From a functional standpoint, signal processing in computer chips is virtually noiseless, conducted at transmission velocities approaching the speed of light, and wholly reproducible from one trial to the next.  In contrast, neurons are both noisy in their signal processing and slow in their signal transmission, while their constitutive components – including the memory-related dendritic spines and axonal boutons – constantly undergo wholesale molecular turnover.  From an architectural standpoint, computers utilize local circuit connectivity in an essentially serial manner, whereas neurons in our brain are highly interconnected for parallel processing (each neuron connects, on average, to 10,000 other neurons).  With this perspective in mind, we propose a uniquely biological theory of motor memory formation based on three assumptions: 1) neural signal processing and synaptic change are both extremely noisy processes, 2) synapses are constantly being modified through learning-dependent mechanisms at extremely high rates (hyperplasticity), and 3) the motor system is highly redundant at all levels.  What emerges from this framework is a unique dynamic interpretation of sensorimotor memory: memories are defined not by fixed patterns of synaptic weights but, rather, by non-stationary synaptic patterns that fluctuate coherently.  The predictions this theory makes are subsequently compared to the known physiological and behavioral properties of the human sensorimotor system.

Host: Dr. Mussa-Ivaldi

Fri, Feb 14

Speaker: Brenna Argall, PhD

Title: Selective and Customizable Autonomy for Rehabilitation Robots

Abstract: For decades, the potential for automation---in particular, in the form of ”smart” wheelchairs---to aid those with motor, or cognitive, impairments has been recognized. The introduction of partial automation makes an assistive machine into a sort of robot, that shares control with the human user. This human-robot team is truly heterogeneous: the goal of the automation is to fill a gap left by the sensory/motor impairment of the user. This talk will identify opportunities for machine learning, artificial intelligence and robot autonomy to be leveraged within rehabilitation and assistive robotics, and overview some ongoing projects within the Argall Research Group.

Tue, Feb 4

Speakers:  Fabrizio Sergi, PhD

Title: Human robotics for gait assistance and clinical neuroscience: two case studies

Host: Dr. Kuiken

Fri, Jan 31

Speakers:  Dr. Chris Marciniak, Dr. Richard Harvey, Kathleen Doherty, and Nathalia Headley

Title: Expert Insights into the IRB

Abstract:   Institutional Review Boards (IRBs) were created to protect people who  volunteer to be in research studies.  The IRB, composed of researchers  and non-scientists, review applications to ensure that the researchers  have designed and planned their studies to minimize patient harms while yielding useful results.  But how does the IRB work and what would be helpful for clinicians and  early career researchers to know about IRB?  The Donnelley Ethics  Program has organized a panel of experienced researchers and IRB members to give you an insight in the workings of an IRB. 

Fri, Jan 24

Speaker: Dr. Milap Sandhu

Title: Intermittent hypoxia and neuroplasticity after spinal cord injury

Abstract:   An important goal of spinal cord injury (SCI) research is to enhance plasticity in the neural pathways spared by the lesion. One experimental strategy for induction of neuroplasticity is brief and repeated exposure to low oxygen, also called “intermittent hypoxia”. Recent studies show that intermittent hypoxia can safely and effectively enhance respiratory and somatic function in both animals and humans after SCI. We are interested in understanding the mechanisms of hypoxia-induced plasticity and developing combinatorial approaches that utilize intermittent hypoxia to improve motor recovery after SCI. I will present data from three different studies which used intermittent hypoxia or related therapies to enhance respiratory function after cervical SCI. First, we studied the impact of intermittent hypoxia on cervical interneurons, which play an important role in the neural circuit remodeling and spontaneous recovery after SCI. Using a multi-array spinal cord recording approach, we show that these interneurons are capable of dynamic reconfiguration during hypoxia.  Similar to respiratory motoneurons, interneurons also showed long term facilitation of activity following intermittent hypoxia. Second, we investigated if a pharmacological agent that activates hypoxia-sensitive carotid chemoafferent neurons can also be used for targeted induction of respiratory neuroplasticity. Our results show that repeated systemic delivery of doxapram, a respiratory stimulant, can trigger robust time-dependent plasticity in the respiratory motor system. In addition, the pattern and magnitude of doxapram-induced facilitation is similar to hypoxia-induced plasticity. Doxapram is an FDA approved drug and may therefore be of use in the context of neurorehabilitation following SCI. Third, we are interested in developing experimental combinatorial approaches using intermittent hypoxia in conjunction with therapies that promote axonal regeneration. To this end, we have shown that hypoxia can modulate the activity of neuronal progenitor cells which have been transplanted into the spinal cord after injury. Furthermore, in related experiments, we have shown that in vitro exposure of neural precursor cells (i.e. partially differentiated stem cells) to intermittent hypoxia can impact their proliferation, survival and differentiation properties. Therefore, intermittent hypoxia may be useful to “prime” donor cells prior to grafting in the spinal cord. In conclusion, plasticity is an important feature of the spared neural pathways after injury, and intermittent hypoxia provides a tool to harness this plasticity and holds promise for use in conjunction with other therapeutic approaches. 

Host: Drs. Jayaraman and Rymer

Fri, Jan 10  **RESCHEDULED from Nov 8

Speaker: Dr. Sean Deeny (from the Rehabilitation Technologies & Outcomes Lab)

Title:  EEG Measures of Cognitive Workload and Cortical Dynamics During Myoelectric Prosthetic Limb Use

Abstract:   A primary goal in development of new myoelectric prosthetic technology is to reduce the cognitive workload or attentional demands of limb control.  Towards that end, the past decade has seen significant advances in prosthetic limb control strategies, prosthetic design, and even surgical techniques, all of which are intended to make prosthesis control as intuitive and functional as possible. However, there are currently no objective and quantitative outcome measures employed in the prosthetics literature to assess cognitive burden of using myoelectric prostheses, or to effectively measure and distinguish the cognitive, perceptual, or motor demands of prosthetic limb use.  We are exploring EEG measures of cortical resource allocation during myoelectric limb control for the purpose of evaluating and guiding new technological advances in “intuitive” prostheses.  We examined the efficacy of event-related potential (ERP) measures of cortical activation as a cognitive workload outcome tool during myoelectric virtual arm control, and compared the cognitive and physical workload of two methods of myoelectric control, direct control (DC) and pattern recognition control (PRC) in sixteen healthy participants with in-tact limbs.  For complicated (3 DOF) movements, PRC was faster and required less muscle activation (EMG), consistent with greater efficiency.  ERP measures of cognitive workload distinguished different levels of difficulty (viewing, 1 DOF, 3 DOF), and distinguished DC from PRC in the 3 DOF condition. We are currently adapting the paradigm to be testing in patients with upper limb and lower limb amputations, and exploring other EEG measures of cortical activation and cortico-cortical communication for future studies.

Host: Dr. Jayaraman   

Fri, Jan 3

Speaker: Dr. Jinsook Roh

Title: Toward muscle coordination-based biological markers for stroke neurorehabilitation

Abstract: How the central nervous system selects which muscles to use from a  mechanically redundant set to complete a motor task is one of the major  unresolved questions in Motor Neuroscience. It is central to understanding both normal  movement and its disruption in neurological disorders. The resulting  scientific knowledge can provide insights on the physiological changes  occurring after neurological injury and form a foundation for innovative translation to develop effective outcome measures in  neuromodulation and neurorehabilitation. Understanding the differences  between normal and pathological neuromuscular coordination schemes can  be utilized to design novel biofeedback of rehabilitative interventions to restore motor functions in stroke survivors. I will  discuss scientific findings on the neural mechanisms of muscle  coordination in animal models and their translation to quantify  abnormalities in muscular coordination in stroke survivors.  

Host: Dr. Rymer