scholarly journals Impaired crossed facilitation of the corticospinal pathway after cervical spinal cord injury

2012 ◽  
Vol 107 (10) ◽  
pp. 2901-2911 ◽  
Author(s):  
Karen L. Bunday ◽  
Monica A. Perez
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Voluntary Contraction ◽  
Facilitatory Effect ◽  
Corticospinal Pathway ◽  
Control Subjects ◽  
Cord Injury ◽  
Healthy Control ◽  
Hand Muscle ◽  
Voluntary Contractions

In uninjured humans, it is well established that voluntary contraction of muscles on one side of the body can facilitate transmission in the contralateral corticospinal pathway. This crossed facilitatory effect may favor interlimb coordination and motor performance. Whether this aspect of corticospinal function is preserved after chronic spinal cord injury (SCI) is unknown. Here, using transcranial magnetic stimulation, we show in patients with chronic cervical SCI (C5–C8) that the size of motor evoked potentials (MEPs) in a resting intrinsic hand muscle remained unchanged during increasing levels of voluntary contraction with a contralateral distal or proximal arm muscle. In contrast, MEP size in a resting hand muscle was increased during the same motor tasks in healthy control subjects. The magnitude of voluntary electromyography was negatively correlated with MEP size after chronic cervical SCI and positively correlated in healthy control subjects. To examine the mechanisms contributing to MEP crossed facilitation we examined short-interval intracortical inhibition (SICI), interhemispheric inhibition (IHI), and motoneuronal behavior by testing F waves and cervicomedullary MEPs (CMEPs). During strong voluntary contractions SICI was unchanged after cervical SCI and decreased in healthy control subjects compared with rest. F-wave amplitude and persistence and CMEP size remained unchanged after cervical SCI and increased in healthy control subjects compared with rest. In addition, during strong voluntary contractions IHI was unchanged in cervical SCI compared with rest. Our results indicate that GABAergic intracortical circuits, interhemispheric glutamatergic projections between motor cortices, and excitability of index finger motoneurons are neural mechanisms underlying, at least in part, the lack of crossed corticospinal facilitation observed after SCI. Our data point to the spinal motoneurons as a critical site for modulating corticospinal transmission after chronic cervical SCI.

scholarly journals Changes in motor-evoked potential latency during grasping after tetraplegia

2019 ◽  
Vol 122 (4) ◽  
pp. 1675-1684 ◽  
Author(s):  
Hang Jin Jo ◽  
Monica A. Perez
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Precision Grip ◽  
Motor Evoked Potential ◽  
Conduction Time ◽  
Corticospinal Pathway ◽  
Cord Injury ◽  
Anterior Posterior

The corticospinal pathway contributes to the control of grasping in intact humans. After spinal cord injury (SCI), there is an extensive reorganization in the corticospinal pathway; however, its contribution to the control of grasping after the injury remains poorly understood. We addressed this question by using transcranial magnetic stimulation (TMS) over the hand representation of the motor cortex to elicit motor-evoked potentials (MEPs) in an intrinsic finger muscle during precision grip and power grip with the TMS coil oriented to induce currents in the brain in the latero-medial (LM) direction to activate corticospinal axons directly and in the posterior-anterior (PA) and anterior-posterior (AP) directions to activate the axon indirectly through synaptic inputs in humans with and without cervical incomplete SCI. We found prolonged MEP latencies in all coil orientations in both tasks in SCI compared with control subjects. The latencies of MEPs elicited by AP relative to LM stimuli were consistently longer during power compared with precision grip in controls and SCI subjects. In contrast, PA relative to LM MEP latencies were similar between tasks across groups. Central conduction time of AP MEPs was prolonged during power compared with precision grip in controls and SCI participants. Our results support evidence indicating that inputs activated by AP and PA currents are engaged to a different extent during fine and gross grasping in humans with and without SCI. NEW & NOTEWORTHY The mechanisms contributing to the control of hand function in humans with spinal cord injury (SCI) remain poorly understood. Here, we demonstrate for the first time that the latency of corticospinal responses elicited by transcranial magnetic stimulation anterior-posterior induced currents, relative to latero-medial currents, was prolonged during power compared with precision grip in humans with and without SCI. Gross grasping might represent a stragegy to engage networks activated by anterior-posterior currents after SCI.

scholarly journals Bilateral reach-to-grasp movement asymmetries after human spinal cord injury

2016 ◽  
Vol 115 (1) ◽  
pp. 157-167 ◽  
Author(s):  
Finnegan J. Calabro ◽  
Monica A. Perez
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Emg Activity ◽  
Small Object ◽  
Functional Impairments ◽  
Reach To Grasp ◽  
Control Subjects ◽  
Cord Injury ◽  
Opening And Closing ◽  
Hand Opening

Cervical spinal cord injury (SCI) in humans typically damages both sides of the spinal cord, resulting in asymmetric functional impairments in the arms. Despite this well-accepted notion and the growing emphasis on the use of bimanual training strategies, how movement of one arm affects the motion of the contralateral arm after SCI remains unknown. Using kinematics and multichannel electromyographic (EMG) recordings we studied unilateral and bilateral reach-to-grasp movements to a small and a large cylinder in individuals with asymmetric arm impairments due to cervical SCI and age-matched control subjects. We found that the stronger arm of SCI subjects showed movement durations longer than control subjects during bilateral compared with unilateral trials. Specifically, movement duration was prolonged when opening and closing the hand when reaching for a large and a small object, respectively, accompanied by deficient activation of finger flexor and extensor muscles. In subjects with SCI interlimb coordination was reduced compared with control subjects, and individuals with lesser coordination between hands were those who showed prolonged times to open the hand. Although the weaker arm showed movement durations during bilateral compared with unilateral trials that were proportional to controls, the stronger arm was excessively delayed during bilateral reaching. Altogether, our findings demonstrate that during bilateral reach-to-grasp movements the more impaired arm has detrimental effects on hand opening and closing of the less impaired arm and that they are related, at least in part, to deficient control of EMG activity of hand muscles. We suggest that hand opening might provide a time to drive bimanual coordination adjustments after human SCI.

scholarly journals Assessment of Hyperactive Reflexes in Patients with Spinal Cord Injury

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Dali Xu ◽  
Xin Guo ◽  
Chung-Yong Yang ◽  
Li-Qun Zhang
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Patellar Tendon ◽  
Knee Extension ◽  
Clinical Settings ◽  
Tendon Reflex ◽  
Cord Injury ◽  
Reflex Gain ◽  
Healthy Control ◽  
Tendon Reflexes

Hyperactive reflexes are commonly observed in patients with spinal cord injury (SCI) but there is a lack of convenient and quantitative characterizations. Patellar tendon reflexes were examined in nine SCI patients and ten healthy control subjects by tapping the tendon using a hand-held instrumented hammer at various knee flexion angles, and the tapping force, quadriceps EMG, and knee extension torque were measured to characterize patellar tendon reflexes quantitatively in terms of the tendon reflex gain (Gtr), contraction rate (Rc), and reflex loop time delay (td). It was found that there are significant increases inGtrandRcand decrease intdin patients with spinal cord injury as compared to the controls (P<0.05). This study presented a convenient and quantitative method to evaluate reflex excitability and muscle contraction dynamics. With proper simplifications, it can potentially be used for quantitative diagnosis and outcome evaluations of hyperreflexia in clinical settings.

scholarly journals Cerebellar contribution to sensorimotor adaptation deficits in humans with spinal cord injury

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yuming Lei ◽  
Monica A. Perez
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Hand Movement ◽  
Cerebellar Atrophy ◽  
Reaching Movements ◽  
Sensorimotor Adaptation ◽  
Post Injury ◽  
Control Subjects ◽  
Learning Rates ◽  
Cord Injury

AbstractHumans with spinal cord injury (SCI) show deficits in associating motor commands and sensory feedback. Do these deficits affect their ability to adapt movements to new demands? To address this question, we used a robotic exoskeleton to examine learning of a sensorimotor adaptation task during reaching movements by distorting the relationship between hand movement and visual feedback in 22 individuals with chronic incomplete cervical SCI and 22 age-matched control subjects. We found that SCI individuals showed a reduced ability to learn from movement errors compared with control subjects. Sensorimotor areas in anterior and posterior cerebellar lobules contribute to learning of movement errors in intact humans. Structural brain imaging showed that sensorimotor areas in the cerebellum, including lobules I–VI, were reduced in size in SCI compared with control subjects and cerebellar atrophy increased with increasing time post injury. Notably, the degree of spared tissue in the cerebellum was positively correlated with learning rates, indicating participants with lesser atrophy showed higher learning rates. These results suggest that the reduced ability to learn from movement errors during reaching movements in humans with SCI involves abnormalities in the spinocerebellar structures. We argue that this information might help in the rehabilitation of people with SCI.

scholarly journals Voluntary Modulation of Evoked Responses Generated by Epidural and Transcutaneous Spinal Stimulation in Humans with Spinal Cord Injury

2021 ◽  
Vol 10 (21) ◽  
pp. 4898
Author(s):  
Jonathan S. Calvert ◽  
Megan L. Gill ◽  
Margaux B. Linde ◽  
Daniel D. Veith ◽  
Andrew R. Thoreson ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Lower Extremity ◽  
Maximum Voluntary Contraction ◽  
Low Frequency ◽  
Voluntary Contraction ◽  
Evoked Responses ◽  
Lumbosacral Spinal Cord ◽  
Lower Extremity Muscle ◽  
Cord Injury

Transcutaneous (TSS) and epidural spinal stimulation (ESS) are electrophysiological techniques that have been used to investigate the interactions between exogenous electrical stimuli and spinal sensorimotor networks that integrate descending motor signals with afferent inputs from the periphery during motor tasks such as standing and stepping. Recently, pilot-phase clinical trials using ESS and TSS have demonstrated restoration of motor functions that were previously lost due to spinal cord injury (SCI). However, the spinal network interactions that occur in response to TSS or ESS pulses with spared descending connections across the site of SCI have yet to be characterized. Therefore, we examined the effects of delivering TSS or ESS pulses to the lumbosacral spinal cord in nine individuals with chronic SCI. During low-frequency stimulation, participants were instructed to relax or attempt maximum voluntary contraction to perform full leg flexion while supine. We observed similar lower-extremity neuromusculature activation during TSS and ESS when performed in the same participants while instructed to relax. Interestingly, when participants were instructed to attempt lower-extremity muscle contractions, both TSS- and ESS-evoked motor responses were significantly inhibited across all muscles. Participants with clinically complete SCI tested with ESS and participants with clinically incomplete SCI tested with TSS demonstrated greater ability to modulate evoked responses than participants with motor complete SCI tested with TSS, although this was not statistically significant due to a low number of subjects in each subgroup. These results suggest that descending commands combined with spinal stimulation may increase activity of inhibitory interneuronal circuitry within spinal sensorimotor networks in individuals with SCI, which may be relevant in the context of regaining functional motor outcomes.

Motor Unit Discharge Characteristics during Voluntary Contraction in Patients with Incomplete Spinal Cord Injury

1999 ◽  
Vol 84 (6) ◽  
pp. 1151-1160 ◽  
Author(s):  
Hazel C. Smith ◽  
Nick J. Davey ◽  
Gordana Savic ◽  
David W. Maskill ◽  
Peter H. Ellaway ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Motor Unit ◽  
Voluntary Contraction ◽  
Incomplete Spinal Cord Injury ◽  
Unit Discharge ◽  
Discharge Characteristics ◽  
Cord Injury ◽  
Motor Unit Discharge
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