Feedback and Feedforward Locomotor Adaptations to Ankle-Foot Load in People With Incomplete Spinal Cord Injury

2010 ◽  
Vol 104 (3) ◽  
pp. 1325-1338 ◽  
Author(s):  
Keith E. Gordon ◽  
Ming Wu ◽  
Jennifer H. Kahn ◽  
Brian D. Schmit
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Neural Control ◽  
Stance Phase ◽  
Single Step ◽  
Control Mechanisms ◽  
Effective Interventions ◽  
Cord Injury ◽  
Locomotor Adaptations ◽  
Limb Load

Humans with spinal cord injury (SCI) modulate locomotor output in response to limb load. Understanding the neural control mechanisms responsible for locomotor adaptation could provide a framework for selecting effective interventions. We quantified feedback and feedforward locomotor adaptations to limb load modulations in people with incomplete SCI. While subjects airstepped (stepping performed with kinematic assistance and 100% bodyweight support), a powered-orthosis created a dorisflexor torque during the “stance phase” of select steps producing highly controlled ankle-load perturbations. When given repetitive, stance phase ankle-load, the increase in hip extension work, 0.27 J/kg above baseline (no ankle-load airstepping), was greater than the response to ankle-load applied during a single step, 0.14 J/kg ( P = 0.029). This finding suggests that, at the hip, subjects produced both feedforward and feedback locomotor modulations. We estimate that, at the hip, the locomotor response to repetitive ankle-load was modulated almost equally by ongoing feedback and feedforward adaptations. The majority of subjects also showed after-effects in hip kinetic patterns that lasted 3 min in response to repetitive loading, providing additional evidence of feedforward locomotor adaptations. The magnitude of the after-effect was proportional to the response to repetitive ankle-foot load ( R2= 0.92). In contrast, increases in soleus EMG amplitude were not different during repetitive and single-step ankle-load exposure, suggesting that ankle locomotor modulations were predominately feedback-based. Although subjects made both feedback and feedforward locomotor adaptations to changes in ankle-load, between-subject variations suggest that walking function may be related to the ability to make feedforward adaptations.

scholarly journals Constraints on Stance-Phase Force Production during Overground Walking in Persons with Chronic Incomplete Spinal Cord Injury

2018 ◽  
Vol 35 (3) ◽  
pp. 467-477 ◽  
Author(s):  
Denise M. Peters ◽  
Yann Thibaudier ◽  
Joan E. Deffeyes ◽  
Gila T. Baer ◽  
Heather B. Hayes ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Stance Phase ◽  
Force Production ◽  
Incomplete Spinal Cord Injury ◽  
Overground Walking ◽  
Cord Injury

scholarly journals Ankle Load Modulates Hip Kinetics and EMG During Human Locomotion

2009 ◽  
Vol 101 (4) ◽  
pp. 2062-2076 ◽  
Author(s):  
Keith E. Gordon ◽  
Ming Wu ◽  
Jennifer H. Kahn ◽  
Yasin Y. Dhaher ◽  
Brian D. Schmit
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Muscle Activity ◽  
Stance Phase ◽  
Gait Cycle ◽  
Gluteus Maximus ◽  
Human Locomotion ◽  
Joint Torque ◽  
Cord Injury ◽  
Hip Extension

The purpose of this research was to examine the role of isolated ankle-foot load in regulating locomotor patterns in humans with and without spinal cord injury (SCI). We used a powered ankle-foot orthosis to unilaterally load the ankle and foot during robotically assisted airstepping. The load perturbation consisted of an applied dorsiflexion torque designed to stimulate physiological load sensors originating from the ankle plantar flexor muscles and pressure receptors on the sole of the foot. We hypothesized that 1) the response to load would be phase specific with enhanced ipsilateral extensor muscle activity and joint torque occurring when unilateral ankle-foot load was provided during the stance phase of walking and 2) that the phasing of subject produced hip moments would be modulated by varying the timing of the applied ankle-foot load within the gait cycle. As expected, both SCI and nondisabled subjects demonstrated a significant increase ( P < 0.05) in peak hip extension moments (142 and 43% increase, respectively) when given ankle-foot load during the stance phase compared with no ankle-foot load. In SCI subjects, this enhanced hip extension response was accompanied by significant increases ( P < 0.05) in stance phase gluteus maximus activity (27% increase). In addition, when ankle-foot load was applied either 200 ms earlier or later within the gait cycle, SCI subjects demonstrated significant phase shifts (∼100 ms) in hip moment profile ( P < 0.05; i.e., the onset of hip extension moments occurred earlier when ankle-foot load was applied earlier). This study provides new insights into how individuals with spinal cord injury use sensory feedback from ankle-foot load afferents to regulate hip joint moments and muscle activity during gait.

scholarly journals Neurophysiological Changes After Paired Brain and Spinal Cord Stimulation Coupled With Locomotor Training in Human Spinal Cord Injury

2021 ◽  
Vol 12 ◽  
Author(s):  
Timothy S. Pulverenti ◽  
Morad Zaaya ◽  
Monika Grabowski ◽  
Ewelina Grabowski ◽  
Md. Anamul Islam ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Motor Cortex ◽  
Stance Phase ◽  
Training Session ◽  
H Reflex ◽  
Locomotor Training ◽  
Step Cycle ◽  
Human Spinal Cord ◽  
Cord Injury

Neurophysiological changes that involve activity-dependent neuroplasticity mechanisms via repeated stimulation and locomotor training are not commonly employed in research even though combination of interventions is a common clinical practice. In this randomized clinical trial, we established neurophysiological changes when transcranial magnetic stimulation (TMS) of the motor cortex was paired with transcutaneous thoracolumbar spinal (transspinal) stimulation in human spinal cord injury (SCI) delivered during locomotor training. We hypothesized that TMS delivered before transspinal (TMS-transspinal) stimulation promotes functional reorganization of spinal networks during stepping. In this protocol, TMS-induced corticospinal volleys arrive at the spinal cord at a sufficient time to interact with transspinal stimulation induced depolarization of alpha motoneurons over multiple spinal segments. We further hypothesized that TMS delivered after transspinal (transspinal-TMS) stimulation induces less pronounced effects. In this protocol, transspinal stimulation is delivered at time that allows transspinal stimulation induced action potentials to arrive at the motor cortex and affect descending motor volleys at the site of their origin. Fourteen individuals with motor incomplete and complete SCI participated in at least 25 sessions. Both stimulation protocols were delivered during the stance phase of the less impaired leg. Each training session consisted of 240 paired stimuli delivered over 10-min blocks. In transspinal-TMS, the left soleus H-reflex increased during the stance-phase and the right soleus H-reflex decreased at mid-swing. In TMS-transspinal no significant changes were found. When soleus H-reflexes were grouped based on the TMS-targeted limb, transspinal-TMS and locomotor training promoted H-reflex depression at swing phase, while TMS-transspinal and locomotor training resulted in facilitation of the soleus H-reflex at stance phase of the step cycle. Furthermore, both transspinal-TMS and TMS-transspinal paired-associative stimulation (PAS) and locomotor training promoted a more physiological modulation of motor activity and thus depolarization of motoneurons during assisted stepping. Our findings support that targeted non-invasive stimulation of corticospinal and spinal neuronal pathways coupled with locomotor training produce neurophysiological changes beneficial to stepping in humans with varying deficits of sensorimotor function after SCI.

Ethical Analysis of a Qualitative Researcher's Unease in Encountering a Participant's Existential Ambivalence

2016 ◽  
Vol 34 (1) ◽  
pp. 51-65 ◽  
Author(s):  
Marìa Elisa Moreno-Fergusson ◽  
Pamela J. Grace
Keyword(s):  
Spinal Cord ◽  
Qualitative Research ◽  
Spinal Cord Injury ◽  
Moral Reasoning ◽  
Ethical Analysis ◽  
Traumatic Spinal Cord Injury ◽  
Effective Interventions ◽  
Cord Injury ◽  
Sensitive Issues

Gaining in-depth understanding of the experiences of persons who have suffered traumatic events with physical and psychological sequelae is important for building effective interventions. However, qualitative research of this kind can be emotionally difficult for the researcher whose research interests derive from practice experiences with the population studied. It may be difficult for the researcher to separate the role of inquirer from that of practitioner. We explore this issue using ethical analysis to differentiate the responsibilities of the researcher from those of the clinician. In the first part of the chapter, we provide some background on the population studied and traumatic spinal cord injury and its aftermath as context for the issues raised by the narrative. Then, we describe briefly the first author's research exploring the meaning of bodily changes and embodiment in persons who have suffered a traumatic spinal cord injury. We provide the part of Jack's story that most troubled the researcher and led her to discuss the situation with an ethics colleague. Finally, we use the tools of moral reasoning, ethical analysis, and principles of research ethics to explore the pertinent excerpt of the narrative. The resulting clarifications are laid out for the reader with the intent of assisting other qualitative researchers in determining the extent and limits of their obligations to participants of qualitative studies, especially those that explore sensitive issues.

scholarly journals A new conceptual framework for the integrated neural control of locomotor and sympathetic function: implications for exercise after spinal cord injury

2018 ◽  
Vol 43 (11) ◽  
pp. 1140-1150 ◽  
Author(s):  
Kristine C. Cowley
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Conceptual Framework ◽  
Neural Control ◽  
Neural Circuitry ◽  
The Body ◽  
Sympathetic Function ◽  
Postural Changes ◽  
Cord Injury ◽  
New Research

All mammals, including humans, are designed to produce sustained locomotor movements. Many higher centres are involved in movement, but ultimately these centres act upon a core “rhythm-generating” network within the brainstem-spinal cord. In addition, endurance-based locomotor exercise requires sympathetic neural support to maintain homeostasis and to provide needed metabolic resources. This review focuses on the roles and integration of these 2 neural systems. Part I reviews the cardiovascular, thermoregulatory, and metabolic functions under spinal sympathetic control as revealed by spinal cord injury at different levels. Part II examines the integration between brainstem-spinal sympathetic pathways and the neural circuitry producing motor rhythms. In particular, the rostroventral medulla (RVM) contains the neural circuitry that (i) integrates heart rate, contractility, and blood flow in response to postural changes; (ii) initiates and maintains cardiovascular adaptations for exercise; (iii) provides direct descending innervation to preganglionic neurons innervating the adrenal glands, white adipose tissue, and tissues responsible for cooling the body; (iv) integrates descending sympathetic drive for energy substrate mobilization (lipolysis); and (v) is the relay for descending locomotor commands arising from higher brain centres. A unifying conceptual framework is presented, in which the RVM serves as the final descending supraspinal “exercise integration centre” linking the descending locomotor command signal with the metabolic and homeostatic support needed to produce prolonged rhythmic activities. The role and rationale for an ascending sympathetic and locomotor drive from the lower to upper limbs within this framework is presented. Examples of new research directions based on this unifying framework are discussed.

Single-step functionalization of poly-catecholamine nanofilms for ultra-sensitive immunosensing of ubiquitin carboxyl terminal hydrolase-L1 (UCHL-1) in spinal cord injury

2019 ◽  
Vol 145 ◽  
pp. 111715 ◽  
Author(s):  
Sultan Khetani ◽  
Vinayaraj Ozhukil Kollath ◽  
Erin Eastick ◽  
Chantel Debert ◽  
Arindom Sen ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Single Step ◽  
Cord Injury ◽  
Carboxyl Terminal

Sexuality and Spinal Cord Injury: The Lived Experiences of Intimate Partners

2017 ◽  
Vol 37 (3) ◽  
pp. 125-131 ◽  
Author(s):  
Kate Eglseder ◽  
Barbara Demchick
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Sexual Activity ◽  
Lived Experiences ◽  
Complex Phenomenon ◽  
Intimate Partners ◽  
Sexual Activities ◽  
Effective Interventions ◽  
Cord Injury ◽  
Semistructured Interviews

Although sexuality is an integral aspect of the human experience, individuals who sustain a spinal cord injury (SCI) often receive inadequate education to facilitate successful participation in sexual activities. Intimate partners are often not included in discussions related to sexuality during the rehabilitative process. The purpose of this study was to identify the lived experiences of intimate partners of individuals with SCI related to sexuality. Four intimate partners were selected to participate in semistructured interviews related to their lived experiences of sexuality. Participants identified aspects of SCI, extreme discomfort due to self-perceived sexual norms, and a lack of education as contributors to unsuccessful participation in sexual activity. Coupled sexual activity is a complex phenomenon which includes factors that influence both the injured individuals as well as their intimate partners. To provide effective interventions in addressing sexuality, practitioners should consider the entire issue, the couple.

Neural Control of Hand Movements

Motor Control ◽  
2015 ◽  
Vol 19 (2) ◽  
pp. 135-141
Author(s):  
Monica A. Perez
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Electrical Stimulation ◽  
Healthy Subjects ◽  
Neural Control ◽  
Hand Movements ◽  
Incomplete Spinal Cord Injury ◽  
Voluntary Activity ◽  
Hand Muscles ◽  
Cord Injury

Most of our daily actions involve movements of the hand. The neuronal pathway contributing to the control of hand movements are complex and not yet completely understood. Recent studies highlight how task-dependent changes in cortical and subcortical pathways driven by contralateral and ipsilateral influences may open avenues to further understand the complexity of hand actions in healthy and disease. In the following section studies using transcranial magnetic and electrical stimulation in healthy subjects and in individuals with chronic incomplete spinal cord injury will be highlighted to further understand neuronal pathways involved in the control of voluntary activity by hand muscles.

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