2012 Research Seminars - Rehabilitation Institute of Chicago

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2012 Research Seminars

Fri, Dec 21

Speaker: Young June Shin

Title:  Development of Anthropomorphic Robot Hand for Next Generation Prosthesis

Abstract: In this presentation, two novel actuation principles for prosthetic robot hands will be mainly explained, which are called ’dual-mode twisting actuation, EM joint locking mechanism’. First of all, designinga light-weight and high-speed robot hand with large grasping force is still an unsolved problem. Motivated by the design challenge, I devoted to proposing a design in which speedy motion and large grasping forces are both available, depending on the operational modes. For instance, the output force of a robot finger may not be necessarily large when it moves fast. The robot finger could move slowly if large force is needed. To implement this idea, I proposed a new type of power transmission, referred to as dual-mode actuation with a passive clutch mechanism. Second, the dexterity of the robot hand plays an important role to grasp various objects stably. The usage of a number of the actuators may lead bulky size and heavy weight or weak grasping force of the robot hand. Therefore, EM joint locking mechanism was proposed to achieve highly dexterous motion which allows the enlarged workspace and various postures. Finally, by adopting the proposed actuation principles, a prosthetic robot hand was developed, which has similar performances such as weight, size, and speed compared with human hands. In order to verify the effectiveness of the developed robot hand, the grasping test will be presented

Host: Jon Sensinger

Fri, Dec 14

Speaker: Members of SMPP and CBM Researchers

Title:  Post-Society for Neuroscience Conference: Discussion of Interesting Work

Abstract: Members of SMPP and CBM who attended the Neuroscience 2012 Conference will present studies that captured their attention. Each speaker will present for about 10 minutes.

Fri, Nov 30     

Speaker: Donald Hedeker, Ph.D.

Title:  Longitudinal Data Analysis with Missing Data

Abstract: Methods for analysis of clinical trial data have rapidly advanced in the last twenty years or so. In particular, mixed-effects models, aka multilevel or hierarchical linear models, are increasingly used for analysis of longitudinal data. These methods are more appropriate than traditional ANOVA techniques since they allow for missing data across time and also for a variety of variance-covariance structures of the longitudinal data. Specifically, this class of models can allow for missing outcome data across time, thus permitting analysis of subjects who have incomplete data across time. Extensions to this approach can be used in sensitivity analyses to elucidate the degree to which conclusions may vary as a function of the assumptions regarding the missing data. In particular, the use of mixed-effects pattern-mixture and selection models will be described as augmented approaches that can be used when one suspects that the missing data are not missing at random. These results drawn from each of these approaches will be contrasted using a longitudinal clinical trial for the treatment of schizophrenia.

Host: Jim Patton

Thurs, Nov 29   

Speaker: Carlo De Luca, Ph.D.

Title:  Evolving Notions on the Neural Control of Force

Abstract: For the past three decades we have reported that during voluntary isometric contractions, the firing rate of motoneurons is inversely proportional to their recruitment threshold. This relationship forms a firing rate spectrum with a hierarchal structure that is contrary to that commonly accepted over the past half century.  The previous orthodoxy was established on observations made on electrically stimulated neural responses from anesthetized cats; whereas ours comes from observations made on voluntary contractions in humans. Our observations were made possible via the use of a novel sensor design and sophisticated algorithms capable of decomposing the surface EMG signal into a set of motor unit firing trains in which the firing instances of each action potential can be identified. We were able to formulate equations describing the behavior of the firing rates of the motoneurons in a pool as a function of recruitment threshold and excitation.

Our firing rate spectrum suggests that evolution preferred enhancement of force-prolongation over force smoothness and greater strength.

Then we developed a model using the firing rate equations combined with time varying properties of the motor unit force twitches to investigate the firing rate behavior during simulated sustained contractions. The input consisted of an excitatory signal (excitation) common to all the motor units in a muscle, consistent with the “common drive” property. Motor units responded with a hierarchically structured firing rate spectrum.  Time and force dependent changes in muscle force production were introduced by varying the motor unit force twitches as a function of time, or by varying the number of active motor units. A force feedback adjusted the input excitation maintaining the simulated force at a target level.

The simulations replicates motor unit behavior characteristics similar to those reported in previous empirical studies of sustained contractions, in particular: 1) the initial decrease and subsequent increase of firing rates; 2) the de-recruitment and recruitment of motor units throughout sustained contractions; and 3) the continual increase in the force-fluctuation during a sustained contraction explained by the recruitment of larger motor units as the cause. The model also describes an alternative mechanism for the “reserve capacity” of motor units to generate extraordinary force, and supports the hypothesis that the control of motoneurons remains invariant in both force-varying and sustained isometric contractions.

Host: Zev Rymer

Mon, Nov 19

Speaker: Andrew Pruszynski, Ph.D.

Title:  The brain and periphery as partners in skilled sensorimotor behavior

Abstract: Motor behavior and sensory perception appear effortless but actually reflect a myriad of complex interactions between the mechanical properties of the body and a highly distributed neural circuit. The goal of my research is to explain how the nervous system handles and exploits these interactions when moving the hand and manipulating objects. In this talk I will describe two lines of research that illustrate how, on the one hand, complex processing in the periphery can inform the brain and, on the other hand, how the brain resolves the mechanical details of the periphery. Specifically, I will first describe recent work showing that human tactile afferent neurons, which terminate in the skin, provide the brain with useful information about the high-level geometric features of a contacted object. I will then describe how neurons in monkey primary motor cortex quickly account for the physical interactions between the shoulder and elbow joints during arm movement.

Host: Lee Miller

Fri, Nov 16

Speaker: Bernard Bechara and Members of RIC’s Instrumentation Shop

Title:  Services Provided by RIC’s Instrumentation Shop

Abstract: Informational session about the RIC Instrumentation Shop and the type of services they provide.

Fri, Nov  9

Speaker: Members of SMPP and CBM Researchers

Title:  Post-Society for Neuroscience Conference: Discussion of Interesting Work

Abstract: Members of SMPP and CBM who attended the Neuroscience 2012 Conference in New Orleans, LA will present one or two studies that captured their attention. Each speaker will present for about 5-10 minutes.

Fri, Oct 26

Speaker: Konrad Kording, Ph.D.

Title:  How to write scientific papers

Abstract: I will describe the anatomy of successful papers and how to write them fast.

Fri, Oct 19

Speaker: Dario Farina, Ph.D.

Title:  The Effective Neural Drive to Muscles: Identification of Common Synaptic Inputs to Motor Neurons

Abstract: Oscillatory inputs in various frequency bands, which may have cortical or peripheral origin, are transmitted to the motor neuron output (neural drive to the muscle) and can be identified with linear analysis methods, despite the non-linearity of the individual neurons. It can be demonstrated that linear transmission is possible because the same input is sent to several neurons which effectively act as an array of non-linear samplers. This distribution of common input linearizes the input-output system made by an array of neurons. This mechanism explains the observations of EMG-EMG and EMG-EEG coherence (linear association). As a consequence, the effective drive to the muscle mainly consists in common input components to motor neurons which are further transformed into muscle force by low-pass-filtering with the twitch forces of the motor units. Accordingly, there is a strong association between muscle force and the low frequency common components of motor neuron discharge patterns.

In this talk, I will start by presenting advanced methods for investigating individual motor units in vivo. These methods are based on multi-channel surface and intramuscular electrodes and allow the extraction of the activities of several tens of motor units concurrently active. These methods are used to identify the neural drive to muscles. I will then present studies supporting the almost linear input-output relation of populations of motor neurons and the transmission of inputs from spinal and supraspinal centers to motor neuron output and force generation.

Host: Dr. Rymer

Fri, Oct 5

Speaker: Paolo Mocarelli, Ph.D.

Title:  Thirty five years after the Seveso accidente: Effects of dioxin on human health

Abstract: Dr. Mocarelli will summarize his studies which demonstrated the effects of dioxin on the male reproductive system and other effects. These data are relevant to our knowledge for medical and also for regulatory purposes. Dr. Mocarelli will also discuss the Don Gnocchi Foundation, which is the largest private foundation for rehabilitation in Italy.

Host: Dr. Mussa-Ivaldi

Mon, Sept 24

Speaker: Colin Franz, MD, Ph.D.

Title: Brief Electrical Stimulation for Augmenting Peripheral Nerve Regeneration

Abstract: Peripheral nerve injuries (PNIs) are remarkably common and can result from a variety of causes ranging from penetrating or closed trauma to compression by mass lesions and drug toxicity. Unlike axons in the brain and spinal cord, peripheral axons retain some capacity to regenerate after injury. This has led to the misconception that patients who suffer a PNI should expect a favorable outcome. In fact, the opposite is probably much closer to the truth. For example, the majority of patients who suffer traumatic PNI wait months to years for a recovery of function that is generally incomplete. In many cases regenerating axons fail to re-establish specific connections with their appropriate end organs, which is a critical step required for the restoration of normal sensory and motor performance. Therefore, the development of strategies aimed at increasing the specificity of axon regeneration is an important step towards achieving better clinical outcomes after PNI.

The main focus of this presentation will be to explore the molecular mechanisms involved in axon targeting of regenerating motor neurons in the context of using this understanding to develop better therapeutic approaches. A second, but closely related focus is the basic science rationale underlying the application of activity based therapies to PNI.

Host: CJ Heckman

Fri, Sept 21

Speaker: Nupur Hajela, PT, Ph.D.

Title: Cortical control of spinal reflex circuits during walking in people with and without a spinal cord injury

Abstract: Cortical control of spinal reflex circuits by means of transcranial magnetic stimulation (TMS) has been extensively investigated in humans. Considerable evidence suggests that spinal reflex circuits in humans are prone to cortical control, while sensory afferents affect cortical excitability. Further, it has long been proposed that spinal interneurons mediating reflex actions of flexion reflex afferents (FRA) reinforce voluntary commands from the brain. However, there is no evidence for cortical modulation of the flexion reflex in humans. Accordingly, in the first study we investigated to what extent descending volleys produced by TMS over the leg region of the primary motor cortex affect the excitability of spinal interneurons mediating actions of FRA which was examined in 14 healthy subjects during seated. The effects of TMS applied over the contralateral leg region of the primary motor cortex at 0.9, 1, and 1.2 times the TA motor evoked potentials (MEPs) resting threshold on the TA flexion reflex were established at the conditioning-test (C-T) intervals of -10, -5, 0, 10, 50, and 70 ms. At the C-T intervals of -10 ms, the TA flexion reflex was significantly facilitated. The conditioned flexion reflex returned to control reflex values thereafter, while at the C-T intervals of 50 and 70 ms the flexion reflex was depressed, regardless of the TMS intensity strength. Our results provide evidence that the polysynaptic TA flexion reflex can be modulated by descending cortical volleys evoked by TMS, and the FRA that produce polysynaptic reflex actions on alpha motoneurons are prone to descending control.

In the second study on a person with motor incomplete spinal cord injury (SCI), we established the effects of subthreshold TMS over the primary motor cortex region on the TA long-latency flexion reflex. Measurements were taken before and after training with a robotic exoskeleton device at rest and during assisted stepping. The TA flexion was evoked following non-nociceptive sural nerve stimulation and was conditioned by TMS at 0.9 TA motor evoked potential resting threshold at conditioning-test intervals that ranged from 70 to 130 ms. Before training, subthreshold TMS induced a significant facilitation on the TA flexion reflex which was reversed to depression after training with the subject at rest. During stepping, corticospinal facilitation of the flexion reflex at early and mid-stance before training was replaced with depression at early and mid-swing followed by facilitation at late swing after training. These results suggest that locomotor training reorganizes the cortical control of spinal interneuronal pathways that generate patterned motor activity in the chronic lesioned human spinal cord.

Lastly, we investigated human TA and soleus MEP phase dependent modulation pattern during different body weight support (BWS) stepping in seven subjects on two separate days. The results suggest that during treadmill stepping, the TA and SOL MEP phase-dependent modulation pattern was similar at 0% and 25% BWS, a linear relationship between TA and SOL MEP amplitude and background activity with respective muscles were found. Also, test retest reliability of TMS related measures during stepping were shown. These findings suggest that corticospinal tract involved in TA and soleus MEP modulation pattern are engaged in a physiological manner during treadmill stepping, and that sensory afferent feedback which is obtained from different body loading is not critical for manifestation of the modulation of corticospinal activity during stepping.

Host: Dr. Knikou

 Wed, Aug 15

The company 'AMS Mekatronic' (http://tekrmd.com/) will display their robotic mobility device.

Fri, Aug 3

Speaker: Yun-Seong Song, Ph.D.

Title: "Design, Implementation and Validation of an Exoskeletal robot for Overground Locomotion Studies in Rodents"

Abstract:  Growing interest in robotic treatment of patients with neurological injury motivates the development of therapeutic robots for basic research into recovery. Though humans are the ultimate beneficiaries, basic research frequently involves rodent models of neurological injury, which motivates robotic devices that can interact with rats or mice.

Currently, available hardware for locomotion studies for rodents are built upon treadmills, which simplify the design and implementation but also restricts the scope of allowed experiments. This is largely due to the treadmills single-dimensional movement and the lack of room for any natural/voluntary movement of the animal.

In order to open up new possibilities in locomotion studies in rodents, hardware for locomotion research in rodents is developed. The key concept is to allow maximal freedom of voluntary movement of the animal while providing forceful interaction when necessary. Advantages and challenges of the proposed machine over other existing designs are discussed. Design and implementation issues are presented and discussed, emphasizing on their implications on free, voluntary, movement of the
animal. A live-animal experiment is conducted to verify the design principles. Unconstrained natural movement of the animal is compared with the movement with the overground robot attached. The compact, overground design and back-drivable implementation of this robot will allow novel experiments that involve open-space, free (or interactive) locomotion of the animal.

Host: Dr. Kuiken

Fri, July 27

Speaker: Karen Banai, Ph.D. (Department of Communication Sciences and Disorders, University of Haifa, Israel)

Title: "Anchoring – a domain general factor contributing to the development of reading and language skills?"

Abstract: Anchoring, a short-term dynamic and implicit process that allows individuals to benefit from repetitions of information within stimulus sequences is known to be related to perceptual and reading skills in adults and adolescents. These relationships led to the hypothesis that anchoring plays a causal role in language and reading development. In this talk, data will be presented from experiments designed to test aspects of this hypothesis in preschool children. Findings in typically developing (TD) children demonstrate that anchoring mechanisms are functional across perception and reading-related tasks even prior to the onset of formal reading instruction. Specifically, frequency discrimination, verbal short-term memory, rapid naming and phonological awareness were all better when estimated with tasks that afford anchoring than when estimated under conditions in which anchoring was not possible. Furthermore, in TD children, anchoring accounts for unique variance in letter knowledge, phonological awareness and vocabulary scores. Preliminary findings from children with language-learning problems suggest reduced anchoring effects in this group. Taken together, these data are consistent with the suggestion that anchoring mechanisms that are functional early in development facilitate the acquisition of language and reading-related skills.

Host: Dr. Dvorkin

Tues, June 26

Speaker: Albert C. Lo, MD, Ph.D., CPH. Associate Professor in the Depts of Neurology and Community Health of Brown University, and is an Associate Director of the Center of Excellence for Regenerative and Restorative Medicine at the Providence VA Medical Center.

Title: "The state of robot-assisted gait training for multiple sclerosis"

Please visit his personal webpage for further details: http://research.brown.edu/research/profile.php?id=1192624084

He is board certified by the American Board of Psychiatry and Neurology. 

Fri, June 8

Speaker: Andrew Sawers (University of Washington, Dept of Rehab Medicine)

Title: "Restoring Powered Movements among Individuals with Lower Limb Loss: Insights from Gradual vs. Sudden Training"

Abstract:  The physical rehabilitation of individuals with lower limb loss has traditionally been guided by a device-driven paradigm. While recent years have seen major advances in prosthetic technology, including powered prosthetic feet which can restore propulsive ankle power to physiological levels; little attention has been given to how individuals with lower limb loss should be trained to use these devices. Currently there are no established training strategies for learning to use powered prostheses. A sensible starting point would be to determine how powered movements should be restored; gradually or suddenly? Research in this area may help alleviate locomotor impairments and activity limitations that persist in spite of advances in technology, expand the pool of candidates for powered prosthetic devices beyond the small percentage who make up the most active portion of the patient population, and aid in the development of training algorithms for future powered rehabilitation devices.

In this seminar I will present results from two recent studies which examined how motor learning and locomotor balance control are influenced by a gradual vs. sudden introduction to novel locomotor tasks. The first study examined the ability of adults without impairments to learn a novel locomotor task and maintain balance control following gradual vs. sudden training. Building upon these results, the second study examined the ability of individuals with transtibial limb loss to elicit and control physiological levels of propulsive ankle power from a powered prosthetic foot following gradual or sudden restoration of that propulsive ankle power.

Host: Dr. Rymer

Tue June 5

Speaker: Vennila Krishnan, Ph.D. (Clinical Biomechanics & Rehabilitation Laboratory, University of Chicago)

Title: "Age related differences in the stabilization of swing foot trajectory in frontal plane"

Abstract: Increased gait variability can accompany increased age and has been associated with gait impairment and disability. Of particular importance is the step width variability (SWV) that is seen in frontal plane. Stabilizing the swing foot trajectory in frontal plane contributes to step width and SWV. Thus, in this study we explored stabilization of foot during swing phase of the gait in older and younger adults using the framework of uncontrolled manifold (UCM) analysis. With respect to the swing foot trajectory (performance variable), the UCM analysis divides the variance in the multi-joint configuration space into two subspaces: (1) good variance (VUCM) – that does not affect the swing foot trajectory and (2) bad variance (VORT) – that affects the swing foot trajectory. If VUCM > VORT, it may be concluded that a multi-joint synergy stabilizes the swing foot trajectory. We hypothesized that there would be a kinematic synergy stabilizing (reducing the variance of) the swing foot trajectory in both the groups, the synergy index would be smaller in older adults, and there would be a positive correlation between step width variability (SWV) and VORT. Ten younger and ten older adults walked across an 8-m laboratory walkway at their preferred speed. Kinematic data were collected using the motion capture, and a geometric model was used to derive the frontal plane swing foot trajectory. The results suggest that a multi-joint kinematic synergy stabilized the swing foot trajectory in frontal plane in both groups. There was a transient increase in the synergy index close to the middle of the swing trajectory with its decline towards the end of the swing trajectory in both groups; the modulation was primarily produced by changes in VORT. This observation contradicts the established  positive relation of VORT to the rate of change of the performance variable; it may be related to typical low accuracy constraints on foot placement. The synergy index was smaller in older adults as compared to the younger adults. Finally, there was a positive partial correlation between SWV and VORT, controlled for age at the late swing. Thus, we conclude that normal aging affects the stabilization of the swing foot trajectory in gait which is associated with decreased precision of frontal plane foot placement.

Host: Dr. Mirbagheri

Tue, May 29 .

Speaker: Vicki Gray, MPT, Ph.D.

Title: "The motor control of exercise that emphasis speed post-stroke"

Abstract: To investigate whether a single session of closed kinetic chain (CKC) exercises emphasizing speed post-stroke could evoke changes in motor control and whether these improvements would transfer to improvements in two postural tasks.  The secondary aim was to determine whether open kinetic chain (OKC) exercises in sitting would induce similar changes in the exercises and postural task. The OKC exercises would provide an alternative for individuals not ambulatory post-stroke. Methods:  Thirty-two individuals post-stroke and 32 age- and sex- matched controls performed a single session of 50 fast squats and steps.  Two types of internal perturbations (arm raise/load drop) were used to assess postural responses pre-exercise, post-exercise and 15 minutes after exercises (Retention).  For the OKC exercises eleven individuals post-stroke performed a single session of 50 fast knee and ankle exercises and postural responses were assessed pre-exercise and post-exercise.  Electromyographic (EMG) activity was measured bilaterally in the rectus femoris, biceps femoris, tibialis anterior, and soleus muscles. Result: The squat was performed slower in the stroke group than controls, with impaired temporal coupling between the knee movement and postural sway.  The paretic biceps femoris EMG was delayed with a reduced slope and the paretic rectus femoris EMG area was reduced.  The squat was initiated with the non-paretic leg as a compensatory strategy in the low motor recovery group whereas the paretic leg was used in an adaptive manner in the high motor recovery group.  The temporal coupling improved and EMG area of the paretic tibialis anterior, biceps femoris and rectus femoris increased in the squats.  In the steps, the paretic biceps femoris and rectus femoris EMG area increased in the stepping leg and the paretic soleus and rectus femoris EMG area increased in the stance leg.  The paretic biceps femoris EMG area and slope increased after exercises in the arm raise task.  In the load drop task, the paretic biceps femoris EMG deactivation improved and was retained after 15 minutes.  Weight bearing symmetry also improved with exercise.  The paretic biceps femoris, rectus femoris, tibialis anterior EMG area increased along with an increase in peak velocity and power during the OKC exercises.  The arm acceleration and biceps femoris EMG area increased in the arm raise task.  Conclusion:  This research reveals the positive effects of a single session of CKC and OKC exercises emphasizing speed on motor control post-stroke and the transfer of improvements to a postural task not practiced.

Host: Dr. Rymer

Wed, May 9

Speaker: Howard Poizner, Ph.D. (Institute for Neural Computation and Graduate Program in Neurosciences, University of California, San Diego)

Title: "New Strategies for Studying the Neural Bases of Motor Behavior in Health and Disease

Abstract:  Newly developed methods for the creation of multimodal virtual environments, combined with synchronized recordings of movement and EEG, provide new approaches for investigating naturalistic motor behavior. In one set of studies, we utilize these technologies to examine reaching and grasping in patients with Parkinson’s disease (PD). We have hypothesized that PD motor deficits are of two distinct types, one due to loss of gain resulting in small and slow movements, and the other due to loss of precise, differentiated basal ganglia function resulting in poorly coordinated movement, and, moreover, that these types of deficits are differentially modulated by medication. We tested this hypothesis by having PD patients use two haptic robotic devices to reach to and grasp virtual objects having different centers of mass, and presented at different orientations relative to gravity. PD patients off dopaminergic therapy showed reduced peak reach velocities, reduced peak hand apertures, and increased lift latencies (reduced gain), as well as impaired coordination of hand and arm during the reach and the lift. Dopaminergic therapy significantly improved gain, but not hand-arm coordination. In a second study, we examined how PD patients adapted to a sudden perturbation in the orientation of a virtual object to be grasped.  Eye movements and EEG, as well as limb movements were recorded. Unlike control subjects, PD patients, on or off dopaminergic therapy, failed to smoothly adjust their aperture to the sudden change in object orientation. Moreover, eye-hand coordination was markedly altered in PD, with patients tracking their hands with their gaze perhaps to compensate for imprecise limb proprioception. Finally, we have begun recording EEG and movement while healthy adults freely explore large-scale virtual environments. We are finding oscillations in the theta frequency band, recorded over mid-parietal cortex, that show consistency when subjects walked through a particular location at widely separated times. Remarkably, the strength of these theta-space maps predicted memory for the location of objects within the environment.

Host: Drs. Rymer and Patton

 Fri, May 5

Advanced Neuro Technology will be exhibiting a TMS neuronavigation system (Visor 2) and a complete TMS-compatible 64-channel EEG system (ASA-Lab).  Both systems will be used concurrently with a Magstim stimulator to show full integration capabilities.  A short presentation of the SmartMove Robotized TMS Coil-Positioning System will also take place if there is time after the exhibitions.  ANT will be available for questions and one-on-one discussions after the event.

Visor 2 exhibition – TMS neuronavigation and motor-mapping

  • Online motor-mapping

  • Simultaneous visualization of EMG and MRI

  • Automatic processing of imported MRI (DICOM, Analyze, Nifti) to obtain realistic models of the scalp and the brain

  • Real-time visualization of induced electric field

  • Accuracy check during the session and upon completion
    -          http://www.ant-neuro.com/products/visor2

ASA-Lab exhibition – EEG recorded during TMS

  •  High-quality active-shielding EEG data acquisition

  • WaveGuard EEG caps – quick application for 64-channels

  • No saturation of amp from TMS

  • Short TMS artifact and very quick (<8ms) recovery to clean EEG

  • Simple trigger identification to identify all TMS pulses in data
    -          http://www.ant-neuro.com/products/asa-lab

SmartMove presentation (if available time) - Robotized TMS Coil-Positioning System

  • Rapidly target any point, even a grid-map  or array of points, saving countless hours

  • Perfectly-compensates motion for precision TMS, especially ideal for rTMS

  • Responds to any force on coil, allowing hand placement of coil positioning

  • Import MRI images in every major format, target using neuro-navigation segmentation results

  • Safety parameters ensure complete comfort and control during every TMS session

  • Smooth and steady robotic coil placement, compatible with nearly every TMS coil

  • Choose and log coil targeting location, rotational axis, and distance to scalp
    -          http://www.ant-neuro.com/products/smartmove

 Thur, May 3

Speaker: Tarkeshwar Singh, Ph.D.    Dept. of Kinesiology, Pennsylvania State University

Title: "Effects of thumb and index finger fatigue on hierarchical control and synergies in prehension tasks"

Abstract: We investigated the effects of thumb and index finger fatigue on digit forces and points of their application across multiple repetitions of a static prehensile task. The purpose of this study was to explore the ability of the central nervous system (CNS) to reorganize synergies at two levels of a hypothetical control hierarchy involved in multi-digit prehension under fatigue of a digit. At the higher level of the hierarchy, the total force and moment of force produced on an object are distributed between the thumb (TH) and the virtual finger (VF, an imagined finger with mechanical output equal to the involved fingers of the hand), while at the lower level the VF action is distributed among the four fingers. One group performed a one-minute fatiguing exercise with the thumb (group-thumb) and the second group performed a fatiguing exercise with the index finger (group-index). Following the fatiguing exercise, the subjects repeated the static prehension tasks. Fatiguing exercises caused a significant drop in the normal force (p<0.05) and an increase in the vertical tangential force (p<0.05) of the exercised digit. The contribution of the normal and tangential forces to the total moment also changed during fatigue in a reciprocal way (Fatigue×Group, p<0.001) to keep the handle in static equilibrium. For group-thumb, the normal forces generated a larger counterclockwise moment and the tangential forces generated a larger clockwise moment during fatigue. This trend was reversed for group-index. The safety margin of the thumb decreased significantly for group-thumb (p<0.001). Changes in synergies stabilizing the total grip force were observed at the higher level of control hierarchy (TH-VF) but not at the lower level. The results suggest adaptive adjustments in both mechanical output of the digits and co-variation patterns in multi-digit prehension tasks during fatigue.

Host: Dr. Mirbagheri

Tue, May 1  

Speaker: Farah Zaheer, Ph.D. (Boston University, Sargent College of Healthand Rehabilitation Sciences)

Title: "Adaptation in motor unitactivity with age and physical activity"

Abstract: The hypothesis that age-related alterations to the morphological properties of a motor unit (MU)are accompanied by modifications in their control properties has been supported by data that compared young (24-37 y.o.) and elderly (65-88y.o.) adults (Erim et al. J. Neurophys.,1999). The objective of the present dissertation was to characterize whether such modifications in MU control properties are progressive across a continuum of ages from childhood to senescence, and whether such adaptations are muscle and usage dependent. Multiple concurrently active MUs were assayed from the first dorsal interosseous (FDI) and vastus lateralis (VL) muscles in healthy subjects from 8-86 years of age. Surface EMG (sEMG) signals were acquired while the participants isometrically tracked a trapezoidal force trajectory at 20%, 50% and 80% of their maximal voluntary force capacity. Data were decomposed into MU trains using a recently developed sEMG decomposition procedure (De Luca et al. J. Neurophys.,2006; Nawab et al. J Clin. Neurophys.,2010) that provides a much greater yield (typically 3- 6 X) than that of previous needle sensor based technologies. Results from n=65 subjects (representing approximately 5307 analyzed MUs) indicate that the average firing rates of the earliest recruited MU trains were significantly reduced with increasing age ( p<0.05))for both muscles and the three normalized force levels tested. Characteristics of MU behavior in young children were reported for the first time, and demonstrated unique properties compared to findings in adults and the elderly.   Additionally, those elderly adults who scored at the high end of a physical activity scale deviated least in their firing rate properties from young adults, demonstrating that habitual physical activity can modify the effects of ageing. These findings indicate an age- and usage-dependency to MU control properties that is progressive.

Host: Z. Rymer

Tue, April 24 

Won-Kyung Song, Ph.D. (Korea National Rehabilitation Research Institute)
Un Joo Kim, MD (Korea National Rehabilitation Hospital)
Jung-Yoon Kim, MD (Korea National Rehabilitation Hospital)

Title: "Rehabilitation Research of Korea National Rehabilitation Center with Program Plan in Translational Research of Rehabilitation Robots"

Abstract:  KNRC is the Korea's only national central rehabilitation institute specialized for disability rehabilitation. Korea National Rehabilitation Center consists of Korea National Rehabilitation Hospital and Korea National Rehabilitation Research Institute. In this talk, three presenters talk about following issues:
1.     Introduction to Korea National Rehabilitation Hospital
            by Un Joo Kim, MD (10 minutes)
2.     Research of Korea National Rehabilitation Research Institute
            by Won-Kyung Song, PhD (25 minutes)
3.     Plan of Translational Research for Rehabilitative Robots
            by Jung-Yoon Kim, MD (10 minutes)
4.    Discussion (10~15 minutes)
At first, we will introduce the Korea National Rehabilitation Hospital that has 300 hospital beds. We provide the best rehabilitation medical services for patients in both acute and sub-acute phases in Korea. Second, we will show the research activities for rehabilitative and assistive systems of Korea National Rehabilitation Research Center. We will present the evaluation results of the self-feeding robotic arm for the people with severe disability and 3D motion analysis results of stroke survivors for the upper extremity exercise. In addition, we quickly review other novel projects. Finally, we will mention the new plan for the translational research for the rehabilitation systems including robots. In order to encourage rehabilitative and assistive systems from the bench to the patient's bedside, we are making the novel plan to fill the gap between the technology domain and the clinical domain. We would like to get the feedback from audiences in this plan.

Host: Dr.  Zhang

 Fri, April 20

Speaker: Margaret Duff, Ph.D. (School of Arts, Media, and Engineering & School of Biological and Health Systems Engineering, Arizona State University)

Title: "Mixed Reality Rehabilitation –Engaging and meaningful stroke therapy systems for clinical and home use"
 Abstract:  Recent research in stroke rehabilitation has focused on the development of novel systems that enhance therapy through interactive digital audio and visual feedback environments. One type of environment, mixed reality rehabilitation (MRR), combines motion capture, media computing and smart objects to provide precise kinematic measurements and engaging multimodal feedback for self-assessment during a reaching task. This talk will explore how an MRR system was implemented in a rehabilitation clinic and will present results comparing functional and kinematic outcomes from a group of stroke survivors who received MRR therapy and a group who received standard of care therapy. I will also discuss my current work translating the MRR system to a home-based training system, focusing on the creation an easy-to-use toolkit of tangible objects to sense, assess and provide feedback on different types of hand manipulation tasks.
Host: Dr. Rymer

Tue, April 17

Speaker: Nikolai Gantchev, MD, Ph.D.

Title: "Whole body action from dynamic posture control to desired movement"

Abstract:  Within the years my goal is to possibly understand the "mysterious functions" of the different structures of the Brain responsible for the interaction between the different elements of the Motor Control i.e. Posture control, Movements coordination and Object manipulation. Based on the current technical and scientific advance in knowledge to analyze and assist the physical well-being and quality of life of both healthy and disabled humans. The general goal of studies of Motor Control is to transform our admiration for human movements into knowledge of how desired movement pattern is generated and achieved. Research in Motor Control, i.e. the neural control of Posture and Movement, have occupied positions of importance in physiology, psychology, clinical neurology and physical medicine for over more than a century.  In my talk I will address briefly the first steps in Motor Control development in Bulgaria. Then I will direct my attention to the organization of Natural Goal-Directed whole-body Movements control and corresponding body posture and equilibrium control. Examples of both in healthy subject and disabled persons will be addressed as well.  During the last 20 years the interest has shifted from studying how simple movements are being organized to Natural Goal-Directed whole-body Movements control and corresponding body posture and equilibrium control. In our daily life interacting with the environment is performed by Reach to Grasp Movements. When the body posture control is impaired due to a given pathology this leads to compromise movements coordination and objects manipulation. That is way it is very important to address and understand the mechanisms for disturbed physiology and pathophysiology of different elements of the Motor Control. Based on this we will walk on a paved way to improve the conditions and adapt patient with movement disorders to daily life activities. We can elaborate and propose appropriated rehabilitation strategies for motor control recovery as an output of research of posture control and motor coordination.  We need to consider what the Goals of Dynamic Postural Control is. Orientation i.e. The ability to maintain an appropriate relationship between the body segments and between the body and the environment for a task (Horak & Macpherson, 1996) and Stability The i.e. ability to maintain the position of the body, and specifically, the center of body mass (COM), within specific boundaries of space, referred to as stability limits.  Way of thinking from dynamic postural control – to functional assessment or vice versa?  Proper balancing movements of separate body segments are essential in maintaining upright stance, firstly, to stabilize the body segments, and secondly to enable the necessary dynamic changes of the body. The balancing of the human body is a complicated process, which demands coordination of the sensory, skeletal, muscle and central nervous systems. First, stimuli from visual, vestibular and somatosensory sources are required to contribute information about the body’s position in space. Soon thereafter, coordinated responses to stimuli must be transmitted to the appropriate muscles to produce corrective movements in certain joints to balance a standing position. Related to dynamic postural control our data related to coordination between arm and leg movements during grasping of distant object with stepping will be discussed.  A lot of natural motor tasks involve whole-body movements. They can be described by complex “kinematics synergies”, that actually represent co - ordination between given goal - directed movement and corresponding posture control. These motor tasks are performed usually at standing posture which changes dynamically during task performance. These dynamic changes of the vertical posture control (trunk flexion, knee bending, stepping etc.) can be considered as Dynamic Postural Adjustments (DPAs) (Gantchev and Gantchev, 1996, 1999).
Related to dynamic postural control our data and approach to cerebral palsy (CP) will be discussed.   To perform a skillful smooth coordinated goal directed movement for the children with cerebral palsy (CP) is an elusive goal. The impaired elements of the Motor Control of CP are manifest by abnormal synergies. They can be demonstrated during different aiming tasks. Those motor tasks can be used as follow up functional analysis of development of CP children behavior. In fact studying the aiming tasks in CP children is two folded. First to gain inside into the mechanisms of impaired Motor Control as a function of the Brain lesions. Second the aiming tasks can be included in planed physiotherapeutic procedures in order to improve by appropriate assistance the whole CP children motor performance.

Host: Dr. Rymer

 Fri, April 9

Speaker: Alaa A. Ahmed

Title: "Practice may make perfect but more practice can make you more efficient: The role of metabolic cost in motor learning

Abstract: It is often assumed that the central nervous system controls movements in a manner that minimizes energetic cost. While empirical evidence for actual metabolic minimization exists in locomotion, actual metabolic cost has yet to be measured during motor learning and/or arm reaching. I will present results from our recent study where we measured metabolic power consumption using expired gas analysis, as humans learned novel arm reaching dynamics. We hypothesized that 1) metabolic power would decrease with motor learning and 2) muscle activity and coactivation would parallel changes in metabolic power. By the end of learning, net metabolic power indeed decreased from initial learning. Muscle activity and coactivation also decreased with motor learning. Interestingly, distinct and significant reductions in metabolic power occurred even after muscle activity and coactivation had stabilized and movement changes were small. These results provide the first evidence of actual metabolic reduction during motor learning and for a reaching task. Further, they suggest that muscle activity may not explain changes in metabolic cost as completely as previously thought. Additional mechanisms such as more subtle features of arm muscle activity, changes in activity of other muscles, and/or more efficient neural processes may also underlie the reduction in metabolic cost during motor learning.

Host: Dr. Dhaher

Fri, March 16

Speaker: Prashant Mehta, Associate Professor (Dept. of Mechanical Science & Engineering, Coordinated Science Laboratory, University of Illinois at Urbana-Champaign)

Title: "Bayesian Inference with Oscillator Models: A Possible Role of Neural Rhythms"

Abstract: Prediction is believed to be a fundamentally important computational function for any intelligent system.  Bayesian inference in probability theory is a well-known mechanism to implement prediction.  This has led to historical and recent interest in Bayesian inference for biological sensory systems: The Bayesian model of sensory (e.g., visual) signal processing suggests that the cortical networks in the brain encode a probabilistic 'belief' about reality. The belief state is updated based on comparison between the novel stimuli (from senses) and the internal prediction.

A natural question to ask then is whether there is a rigorous methodology to implement complex forms of prediction via Bayes rule at the level of neurophysiologically plausible spiking elements?  In this talk, I will provide a qualified answer to this question via coupled oscillator models.  A single oscillator is a simplified model of a single spiking neuron.  The coupled oscillator model solves an inference problem:  The population encodes a belief state that is continuously updated (in a Bayes optimal fashion) based on noisy measurements. The methodology is described with the aid of a model problem involving estimation of a 'walking gait cycle' using noisy measurements. This is joint work with several students and collaborators at the University of Illinois. 

Bio:  Prashant Mehta is an Associate Professor in the Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign.  He received his Ph.D. in Applied Mathematics from Cornell University in 2004.  Prior to joining Illinois, he was a Research Engineer at the United Technologies Research Center (UTRC).  His research interests are at the intersection of dynamical systems and control theory, including mean-field games, model reduction, and nonlinear control.  He has received several awards including an Outstanding Achievement Award for his research contributions at UTRC, several Best Paper awards together with his students at Illinois, and numerous teaching and advising honors at Illinois.

Host: Robert D Gregg

Thurs, March 8

Speaker: Farah Zaheer, Ph.D.

Title:"Adaptations in motor unit activity with age and physical activity"

Abstract:  The hypothesis that age-related alterations to the morphological properties of a motor unit (MU) are accompanied by modifications in their control properties has been supported by data that compared young (24-37 y.o.) and elderly (65-88 y.o.) adults (Erim et al. J. Neurophys., 1999). The objective of the present dissertation was to characterize whether such modifications in MU control properties are progressive across a continuum of ages from childhood to senescence, and whether such adaptations are muscle and usage dependent. Multiple concurrently active MUs were assayed from the first dorsal interosseous (FDI) and vastus lateralis (VL) muscles in healthy subjects from 8-86 years of age. Surface EMG (sEMG) signals were acquired while the participants isometrically tracked a trapezoidal force trajectory at 20%, 50% and 80% of their maximal voluntary force capacity. Data were decomposed into MU trains using a recently developed sEMG decomposition procedure (De Luca et al. J. Neurophys., 2006; Nawab et al. J Clin. Neurophys., 2010) that provides a much greater yield (typically 3- 6 X) than that of previous needle sensor based technologies. Results from n=65 subjects (representing approximately 5307 analyzed MUs) indicate that the average firing rates of the earliest recruited MU trains were significantly reduced with increasing age ( p<0.05)) for both muscles and the three normalized force levels tested. Characteristics of MU behavior in young children were reported for the first time, and demonstrated unique properties compared to findings in adults and the elderly.   Additionally, those elderly adults who scored at the high end of a physical activity scale deviated least in their firing rate properties from young adults, demonstrating that habitual physical activity can modify the effects of ageing. These findings indicate an age- and usage-dependency to MU control properties that is progressive.

Host: Dr. Rymer

Thurs, March 1

Speaker: C. Machnes

Title: "Demixing the information contained in neural population responses"

Abstract: Higher brain areas receive inputs from many parts of the brain. The activity of neurons in these areas often reflects this mix of influences. As a result, neural responses are extremely complex and heterogeneous, even in animals performing relatively facile tasks. We propose a data analysis method that provides a succinct description of the population response of these neurons while also extracting, in contrast to PCA and other dimensionality reduction techniques, the relevant task variables from the recordings. We study use of the method, called "demixed PCA", for neural population recordings obtained in monkeys and rodents.

Host: Dr. Kording

Wed, Feb 29 

Speaker: Katherine M. Steele, Ph.D. (Mechanical Engineering, Stanford University)

Title: "The Dynamics of Crouch Gait in Cerebral Palsy: Using musculoskeletal simulation to examine pathologic gait patterns"

Abstract:   Crouch gait is a common gait pathology among individuals with cerebral palsy which is characterized by excessive hip and knee flexion. If left untreated, crouch gait can lead to joint pain, the formation of bone deformities, and an inability to walk independently. While the complexity of the musculoskeletal system hinders the design of effective treatments for crouch gait, musculoskeletal modeling and simulation provide powerful tools to investigate the complex causes and effects of crouch gait. In this talk, I will discuss how we have used musculoskeletal simulation to critically evaluate the dynamics of crouch gait using OpenSim, a freely-available software. I will elaborate on how individual muscles contribute to motion, how joint loads change during crouch gait, and how altered physiology, such as muscle weakness, can contribute to crouch gait. Quantifying these mechanisms in crouch gait can expand our understanding of the causes of crouch gait and create new treatment strategies. The tools and methods presented in this talk can be extended into many other research areas including rehabilitation, athletics, and orthopaedics.

Host: Dr. Patton

Tue, Feb 14

Speaker: Reza Shirazi, Ph.D.

Title: "Finite Element Simulation of Soft Tissues in the Knee Joint"

Abstract:   Practical difficulties and ethical considerations in experimental methods motivate use of computational models as an indispensable complementary tool for assessment of biological tissues and joints. Biological soft tissues such as cartilage and meniscus are strongly anisotropic with tensile-compressive asymmetry. Consequently, the development and implementation of accurate material models that may be used for delineating tissue structure-function relations are challenging tasks. 

During my PhD and postdoctoral studies, I investigated the biomechanics of intact and injured soft tissues and their roles and interactions in the human knee joint by developing state-of-the-art axisymmetric, 2-D, and 3-D finite element models. These computational models were validated against experimental studies at joint, tissue, and intra-tissue levels. Commonly observed perturbations to the knee joint such as meniscal, ligament, cartilage, and bone injuries as well as subsequent surgical interventions such as ligament reconstruction and cartilage repair were simulated by these computational models.  The real-world health care implications of my studies include prosthetic and surgical interventions, rehabilitation strategies, cartilage regeneration, and osteoarthritis treatment.

Host: Dr. Dhaher

Thurs, Feb 9

Speaker: Ajit M. W. Chaudhari, Ph.D. (OSU Department of Orthopaedics, OSU Sports Health & Performance Institute)

Title: "Lumbopelvic Control: What is it, and what role does it play in sports injury and performance?"

Abstract:  Anecdotal data throughout the scientific literature and popular press advocate for improved lumbopelvic control or "core stability" for injury treatment and, more importantly, prevention of injury involving the lower extremity as well as low back and upper extremity. Despite this widespread assertion that "you need to work on your core," a critical barrier to progress in the prevention of musculoskeletal injuries is the lack of understanding of the mechanism by which lumbopelvic control could modulate known biomechanical predictors of injury risk. This talk will discuss the current evidence that exists to define the role of lumbopelvic control in lower extremity mechanics, including recent studies done at Ohio State University and elsewhere exploring this relationship. I will also discuss future research directions to improve our understanding of lower extremity injury mechanisms and accelerate development of more efficient and effective injury prevention programs.

Host: Dr. Dhaher

Fri, Feb, 3

Speaker: Xiao Hu, Graduate Student (Murray/Perreault)

Title: To what extent human can regulate joint mechanics to better control the torque, less affected by position perturbation

Abstract:  Muscle stiffness increases with increasing muscle force, allowing limb stiffness and stability to be increased through changes in co-activation of antagonistic muscles. This intrinsic muscle behavior is appropriate for tasks that require increased stiffness, but would limit the ability decrease limb stiffness in forceful tasks require compliancy, as is true when it is desirable to maintain an accurate force even in the presence of unexpected perturbations. Neural feedback could be used to compensate for these intrinsic muscle properties during force regulation tasks, but the limits on the efficacy of that compensation are not yet clear. The aim of this study is to quantify how well humans can regulate force and how that ability is related to the intrinsic properties of the active muscles and the behavior of the neural controller. Understanding these limits is essential for determining how altered feedback influences the ability to regulate force and for determining how to best construct man-machine interfaces that allow for forceful interactions between the human body and the environment. This study has both modeling and experimental components, both focused on the regulation of human elbow mechanics. Our preliminary results demonstrate that humans can voluntarily reduce stiffness to assist in the regulation of torque. This compensation for the intrinsic properties of the active muscles appears to rely on rapid feedback pathways operating within the range of 100-150 ms.

Mon, Feb 2

Speaker: Linda Resnik, PT, Ph.D.

Title: "VA Studies of the DEKA Arm: Preliminary Findings and Future Plans"

Abstract:  Since 2008 the VA has partnered with DARPA to conduct a multi-site study to optimize the DEKA Arm, one of the two prototype advanced upper limb prosthetic devices developed under DARPA's Revolutionizing Prosthetics Program.  The DEKA Arm was designed for users with amputations at the forequarter, shoulder disarticulation, transhumeral or transradial levels. It has 6 pre-programmed hand grips (power, chuck, lateral pinch, open pinch, closed pinch and tool grip). The full DEKA Arm system has 10 powered degrees of movement.  Users have a variety of control options including EMGs, air bladders, and foot controls (Force Sensitive Resistors (FSR) and Inertial Measurement Units (IMUs)).

The overall purpose of the VA study is to evaluate usability of the Generation 2 and Generation 3 DEKA Arm prototypes and provide feedback to DEKA Integrated Solutions (DISC) to inform optimization efforts.  In this presentation, Dr. Resnik will provide an overview of the VA optimization study design, share preliminary findings from the Generation 2 portion of the study, and discuss the VA's immediate plans to initiate a take home study of the Generation 3 prototype.

Host: Dr. Jayaraman

Wed, Feb 1

Speaker: Alejandro Melendez. Ph.D.. Imperial College London

Title: Investigating sensory-motor interactions to shape rehabilitation

Abstract:   Over the last decades, robotic devices for neurorehabilitation have been developed with the aim of providing better and faster improvement of motor performance. These devices are being used to help patients repeat movements and (re)learn different dynamic tasks. Over the years, these devices have become bigger and more complex, so as to provide the end user with a more realistic and sophisticated stimuli while still allowing the experimenter to have control over the interaction forces that can potentially shape the motor behaviour. However, experimental results have shown no clear advantage of these complex devices over simpler versions. In this context, at the Human Robotics group at Imperial College, we investigate sensory-motor processes of human interaction which can help us understand the main issues for rehabilitation devices and how to overcome the limitations of simple devices to train particular motor behaviours without compromising recovery. In this talk I will present recent findings from my two lines of research under this philosophy:   i) visual cues to compensate for proprioception and ii) mechanisms of human-human physical interaction.

Ad i): Learning a novel skill requires integration of different sensory modalities, in particular vision and proprioception. Hence, one can expect that learning will depend on the mechanical characteristics of the device. For instance, a device with limited degrees of freedom will reduce the amount of information about the environment, modify the dynamics of the task and prevent certain error-based corrections.  To investigate this, the first part of my talk will present results on how the lack of proprioceptive feedback that is created due to mechanical constraints can be substituted with visual information.

Ad ii): Conventional neurorehabilitation of motor function relies on haptic interaction between the patient and physiotherapist. However, how humans deal with human-human interactions is largely unknown, and has been little studied.  In this regard, I will present experiments on how we investigate the mechanisms of interaction during human-human collaborative tasks. I will show results on how we identify the different approaches that dyads can take, and how implicit visual cues can be used to induce particular dyad behaviours and help us tackling the analysis of haptic interactions.
Host: Dr. Patton

Fri, Jan 27

Speaker:  Emily Oby

Title:  Muscle-like neurons for a muscle-like BMI

Abstract:  Brain-Machine Interfaces (BMIs) have the potential to restore motor function lost due to disease or injury by using neural signals to drive an actuator.   Most current BMI research focuses on primary motor cortical (M1) signals used for kinematic control of a computer cursor or a robotic arm that mimics movement of the hand.   However, the discharge of nearly all M1 neurons is also modulated by the posture of the arm and applied forces. In one previous study, forearm rotation between the prone and supine positions was used to alter the pulling direction of the muscles that mediate wrist movements. This manipulation revealed two distinct groups of neurons: “intrinsic” neurons whose directional tuning curves changed much like those of muscles, and “extrinsic” neurons whose tuning curves remained fixed in space.   This heterogeneous distribution of neurons has obvious implications for the design of BMIs intended to control either the kinematics or dynamics of movement across varying loads and limb postures.

To further examine this question, we trained 4 monkeys to perform a 2D isometric wrist center-out task, in which the monkey moved a computer cursor from a central target to one of eight peripheral targets by exerting torque in different directions about the wrist.   We recorded M1 neurons using a multi-electrode array with the monkey’s arm in different forearm postures.   We fit tuning curves during the force hold period, and characterized each neuron based on how its preferred direction changed as a function of forearm orientation.  Unlike the earlier study, we found a single population of M1 neurons, whose preferred directions rotated much like those of muscles.

If the dynamics of most M1 signals are comparable to those of muscle activity, a BMI designed to drive an actuator with dynamics like those of muscles might be more robust, require less time to learn than a kinematic BMI, and generalize across postures better. With this in mind, we are developing a BMI to restore hand use through cortically-controlled functional electrical stimulation of hand and forearm muscles.

Speaker: Brian London

Title: Cortical Representations of Proprioception

Abstract:  Many investigators use velocity dependent force fields to investigate motor adaptation and neural control of movement. Here we describe a velocity dependent representation of force in primary somatosensory cortex (S1).  Limb state information is forwarded to the brain from muscle spindles, which detect position and velocity, and Golgi tendon organs, which detect force.  Much electrophysiology work has been done to describe the firing properties of individual cells.  Often S1 cells are described in terms of the receptors types that resemble their responses, or as additive combinations of multiple receptor types. Here we show cells in S1 encoding a non-linear combination of force and velocity.  This response contains a direction independent representation of the amount of resistance (or assistance) an outside load is providing to a particular movement.

Fri, Jan 13

Speaker: Laura Gingrich, Ph.D.

Title: Lingual-palatal pressures in healthy adults and persons with parkinson's disease

Abstract:  Swallowing impairment, or dysphagia, is a common comorbidity for many neurological populations, and may exert a large influence on rehabilitation outcomes. Therefore, early identification and treatment of dysphagia is imperative in rehabilitation settings.  Reduced lingual-palatal pressures have been documented in many clinical populations with dysphagia. Understanding normal parameters and variability within the context of aging may help identify individuals who may be vulnerable to lingual weakness, and may distinguish normal age-related changes from disordered lingual function. Dr. Gingrich will present her research exploring lingual-palatal pressure generation with consideration of the effects of age, gender, and the relation between oral/palatal dimensions in healthy adults. As a clinical correlate, lingual-palatal pressures for persons with Parkinson's Disease (PD) during high and low dopaminergic medication states will also be presented in comparison to healthy controls. Dysphagia is common in persons with PD, resulting in a high risk of aspiration pneumonia, which is the second most frequently cited cause of death for persons with PD.

Host: Dr. Cherney

Mon, Jan 9 

Speaker: Sabrina Lee, Ph.D.

Title: Influence of musculoskeletal architecture and motor unit recruitment on locomotor performance

Abstract: Classic research in comparative functional morphology suggests that  musculoskeletal architectural parameters (such as muscle fascicle length, pennation angle, muscle thickness, and moment arm), composition, and specific motor unit recruitment of many animals allow them to achieve maximal performance. While these variables have been shown to influence function in animals, the relationships between musculoskeletal architecture, motor unit recruitment, and locomotor performance are not well established in many human movements. In this talk, I will discuss my work investigating these relationships in human populations that have obvious different functional demands: sprinters, older adults, and individuals with spinal cord injuries. Using a variety of techniques such as ultrasound imaging, electromyography and wavelet analysis, gait analysis, and modeling allows an integrative approach to provide insight into the influence of musculoskeletal architecture and motor unit recruitment on locomotor performance. This will form the basis for proposing realistic clinical tools used to aid in prevention of injuries and mobility loss in older adults and to aid in diagnosing and implementing interventions for individuals with spinal cord injuries.

Host: Dr. Mirbagheri