1,721,015 research outputs found
Spatiotemporal Dynamics of Online Motor Correction Processing Revealed by High-density Electroencephalography
No full textThe ability to control online motor corrections is key to dealing with unexpected changes arising in the environment with which we interact. How the CNS controls online motor corrections is poorly understood, but evidence has accumulated in favor of a submovement-based model in which apparently continuous movement is segmented into distinct submovements. Although most studies have focused on submovements' kinematic features, direct links with the underlying neural dynamics have not been extensively explored. This study sought to identify an electroencephalographic signature of submovements. We elicited kinematic submovements using a double-step displacement paradigm. Participants moved their wrist toward a target whose direction could shift mid-movement with a 50% probability. Movement kinematics and cortical activity were concurrently recorded with a low-friction robotic device and high-density electroencephalography. Analysis of spatiotemporal dynamics of brain activation and its correlation with movement kinematics showed that the production of each kinematic submovement was accompanied by (1) stereotyped topographic scalp maps and (2) frontoparietal ERPs time-locked to submovements. Positive ERP peaks from frontocentral areas contralateral to the moving wrist preceded kinematic submovement peaks by 220–250 msec and were followed by positive ERP peaks from contralateral parietal areas (140–250 msec latency, 0–80 msec before submovement peaks). Moreover, individual subject variability in the latency of frontoparietal ERP components following the target shift significantly predicted variability in the latency of the corrective submovement. Our results are in concordance with evidence for the intermittent nature of continuous movement and elucidate the timing and role of frontoparietal activations in the generation and control of corrective submovements.National Institutes of Health (U.S.) (R01-HD045343)National Institutes of Health (U.S.) (R01-NS036449)United States. Office of Naval Research. Multidisciplinary University Research Initiative (Award N000140811114)National Science Foundation (U.S.) (Grant SMA-1041755)onal Science Foundation (U.S.). Office of Emerging Frontiers in Research and Innovation (ENG-1137279
Pointing with the ankle: the speed-accuracy trade-off
No full textThis study investigated the trade-off between speed and accuracy in pointing movements with the ankle during goal-directed movements in dorsal–plantar (DP) and inversion–eversion (IE). Nine subjects completed a series of discrete pointing movements with the ankle between spatial targets of varying difficulty. Six different target sets were presented, with a range of task difficulty between 2.2 and 3.8 bits of information. Our results demonstrated that for visually evoked, visually guided discrete DP and IE ankle pointing movements, performance can be described by a linear function, as predicted by Fitts’ law. These results support our ongoing effort to develop an adaptive algorithm employing the speed-accuracy trade-off concept to control our pediatric anklebot while delivering therapy for children with cerebral palsy.Cerebral Palsy International Research Foundation (CPIRF)Stavros S. Niarchos FoundationBaltimore VA Medical Center (contract 512-D05015)National Institutes of Health (U.S.) (NIH Grant R01HD069776-02)Foundation for Education and European Culture (IPEP
Reaction time in ankle movements: a diffusion model analysis
No full textReaction time (RT) is one of the most commonly used measures of neurological function and dysfunction. Despite the extensive studies on it, no study has ever examined the RT in the ankle. Twenty-two subjects were recruited to perform simple, 2- and 4-choice RT tasks by visually guiding a cursor inside a rectangular target with their ankle. RT did not change with spatial accuracy constraints imposed by different target widths in the direction of the movement. RT increased as a linear function of potential target stimuli, as would be predicted by Hick–Hyman law. Although the slopes of the regressions were similar, the intercept in dorsal–plantar (DP) direction was significantly smaller than the intercept in inversion–eversion (IE) direction. To explain this difference, we used a hierarchical Bayesian estimation of the Ratcliff’s (Psychol Rev 85:59, 1978) diffusion model parameters and divided processing time into cognitive components. The model gave a good account of RTs, their distribution and accuracy values, and hence provided a testimony that the non-decision processing time (overlap of posterior distributions between DP and IE < 0.045), the boundary separation (overlap of the posterior distributions < 0.1) and the evidence accumulation rate (overlap of the posterior distributions < 0.01) components of the RT accounted for the intercept difference between DP and IE. The model also proposed that there was no systematic change in non-decision processing time or drift rate when spatial accuracy constraints were altered. The results were in agreement with the memory drum hypothesis and could be further justified neurophysiologically by the larger innervation of the muscles controlling DP movements. This study might contribute to assessing deficits in sensorimotor control of the ankle and enlighten a possible target for correction in the framework of our on-going effort to develop robotic therapeutic interventions to the ankle of children with cerebral palsy.Cerebral Palsy International Research Foundation (CPIRF)Stavros Niarchos FoundationBaltimore VA Medical Center (contract 512-D05015)National Institutes of Health (U.S.) (NIH Grant R01HD069776-02)Education and European Culture Foundatio
Robotic Therapy: The Tipping Point
Get PDFThe last two decades have seen a remarkable shift in the neurorehabilitation paradigm. Neuroscientists and clinicians moved away from the perception that the brain is static and hardwired to a new dynamic understanding that plasticity is a fundamental property of the adult human brain and might be harnessed to remap or create new neural pathways. Capitalizing on this innovative understanding, the authors introduced a paradigm shift in the clinical practice in 1989 when they initiated the development of the Massachusetts Institute of Technology-Manus robot for neurorehabilitation and deployed it in the clinic in 1994 (Krebs et al. 1998). Since then, the authors and others have developed and tested a multitude of robotic devices for stroke, spinal cord injury, cerebral palsy, multiple sclerosis, and Parkinson disease. Here, the authors discuss whether robotic therapy has achieved a level of maturity to justify its broad adoption in the clinical realm as a tool for motor recovery.National Institutes of Health (U.S.) (Grant 1 R01-HD045343)Baltimore Veterans Affairs Medical Cente
Linear Time-Varying Identification of Ankle Mechanical Impedance During Human Walking
No full textThis paper presents a new method to investigate the multivariable time-varying behavior of the ankle during human walking, and provides the first experimental results from treadmill walking. A wearable ankle robot with an ensemblebased linear time-varying system identification method enabled identification of transient ankle mechanical impedance in 2 degrees of freedom, both in the sagittal and frontal planes. Several important issues of the ensemble-based identification method in practical measurements are discussed, especially a strategy to solve the limitation of the method which assumes that the system undergoes the same time-varying behavior on every stride. The suggested method was successfully applied to 15 minutes of human walking on a treadmill. Experiments with 10 young healthy subjects showed clear time-varying behavior of ankle impedance across the gait cycle, except the mid-stance phase. Interestingly, most subjects increased ankle impedance just before heel strike in both degrees of freedom. Interpretation of impedance changes was consistent with analysis of electromyographic signals from major muscles related to ankle movements.Toyota Motor Corporation. Partner Robot DivisionGloria Blake Endowment FundSamsung Fellowshi
The effect of repeated measurements using an upper extremity robot on healthy adults
No full textWe are expanding the use of the MIT-MANUS robotics to persons with impairments due exclusively to orthopedic disorders, with no neurological deficits. To understand the reliability of repeated measurements of the robotic tasks and the potential for registering changes due to learning is critical. Purposes of this study were to assess the learning effect of repeated exposure to robotic evaluations and to demonstrate the ability to detect a change in protocol in outcome measurements. Ten healthy, unimpaired subjects (mean age = 54.1 +/- 6.4 years) performed six repeated evaluations consisting of unconstrained reaching movements to targets and circle drawing (with and without a visual template) on the MITMANUS. Reaching outcomes were aiming error, mean and peak speed, movement smoothness and duration. Outcomes for circle drawing were axis ratio metric and shoulder- elbow joint angles correlation metric (was based on a two-link model of the human arm and calculated hand path during the motions). Repeated-measures ANOVA (p < or = .05) determined if difference existed between the sessions. Intraclass correlations (R) were calculated. All variables were reliable, without learning across testing sessions. Intraclass correlation values were good to high (reaching, R > or =.80; circle drawing, R > or =.90). Robotic measurement ability to differentiate between similar but distinct tasks was demonstrated as measured by axis ratio metric (p < .001) and joint correlation metric (p = .001). Outcome measures of the MIT-MANUS proved to be reliable yet sensitive to change in healthy adults without motor learning over the course of repeated measurement
Robotics: A Rehabilitation Modality
Get PDFA novel rehabilitation technique must demonstrate certain attributes, namely
demonstrate GAINS at the end of intervention, PERSIST beyond treatment, show
evidence of GENERALIZATION, reduce COST, or demonstrate cost/benefit
advantages. Upper extremity robotics is a novel post-stroke rehabilitative
modality as it has already demonstrated these attributes. Lower extremity
robotics has yet to demonstrate the same attributes. We are highly optimistic
that with careful research basic on solid neuroscience principles, we can
improve outcomes for lower extremity robotics as a rehabilitative modality
On the control of the MIT-Skywalker
No full textWalking impairments are a common sequela of
neurological injury, severely affecting the quality of life of both
adults and children. Gait therapy is the traditional approach to
ameliorate the problem by re-training the nervous system and
there have been some attempts to mechanize such approach. In
this paper, we present a novel device to deliver gait therapy,
which, in contrast to previous approaches, takes advantage of
the concept of passive walkers and the natural dynamics of the
lower extremity in order to deliver more “ecological” therapy.
We also discuss the closed-loop control scheme, which enables
safe and efficient operation of the device, and present the initial
feasibility tests with unimpaired subjects.Stavros S. Niarchos FoundationCerebral Palsy International Research Foundatio
MIT-skywalker
No full textThe ability to walk is important for independent living and when this capacity is affected by neurological injury, gait therapy is the traditional approach to re-train the nervous system. The importance of this problem is illustrated by the approximately 5.8 million stroke survivors alive in the US today and an estimated additional 700,000 strokes occurring each year, many requiring gait therapy. This manuscript presents the design and proof-of-concept testing for a novel device to deliver gait therapy. While robotic devices to train gait therapy exist, none of them take advantage of the concept of passive walkers and most of them impose the kinematics of unimpaired gait on impaired walkers. Yet research has found that proper neural input and stimulation is a critical factor for an efficacious therapy program. This novel device might afford a more ecological gait therapy including heel-strike
A working model of stroke recovery from rehabilitation robotics practitioners
Get PDFWe reviewed some of our initial insights about the process of upper-limb behavioral recovery following stroke. Evidence to date indicates that intensity, task specificity, active engagement, and focusing training on motor coordination are key factors enabling efficacious recovery. On modeling, experience with over 400 stroke patients has suggested a working model of recovery similar to implicit motor learning. Ultimately, we plan to apply these insights in the development of customized training paradigms to enhance recovery.NYSCORENational Institute of Child Health and Human Development - National Center for Medical Rehabilitation Research (Grant # 1 R01-HD045343)VA Veterans Affairs (Grants # B3688R, B3607R
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