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1.
Nat Neurosci ; 23(3): 363-374, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32066987

RESUMO

Recent reports have revealed that oligodendrocyte precursor cells (OPCs) are heterogeneous. It remains unclear whether such heterogeneity reflects different subtypes of cells with distinct functions or instead reflects transiently acquired states of cells with the same function. By integrating lineage formation of individual OPC clones, single-cell transcriptomics, calcium imaging and neural activity manipulation, we show that OPCs in the zebrafish spinal cord can be divided into two functionally distinct groups. One subgroup forms elaborate networks of processes and exhibits a high degree of calcium signaling, but infrequently differentiates despite contact with permissive axons. Instead, these OPCs divide in an activity- and calcium-dependent manner to produce another subgroup, with higher process motility and less calcium signaling and that readily differentiates. Our data show that OPC subgroups are functionally diverse in their response to neurons and that activity regulates the proliferation of a subset of OPCs that is distinct from the cells that generate differentiated oligodendrocytes.


Assuntos
Bainha de Mielina/fisiologia , Células Precursoras de Oligodendrócitos/fisiologia , Animais , Animais Geneticamente Modificados , Sinalização do Cálcio/fisiologia , Diferenciação Celular , Divisão Celular , Linhagem da Célula , Proliferação de Células , Embrião não Mamífero/fisiologia , Rede Nervosa/citologia , Rede Nervosa/fisiologia , Medula Espinal/citologia , Medula Espinal/fisiologia , Natação/fisiologia , Peixe-Zebra
2.
Physiol Rev ; 100(1): 271-320, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31512990

RESUMO

The vertebrate control of locomotion involves all levels of the nervous system from cortex to the spinal cord. Here, we aim to cover all main aspects of this complex behavior, from the operation of the microcircuits in the spinal cord to the systems and behavioral levels and extend from mammalian locomotion to the basic undulatory movements of lamprey and fish. The cellular basis of propulsion represents the core of the control system, and it involves the spinal central pattern generator networks (CPGs) controlling the timing of different muscles, the sensory compensation for perturbations, and the brain stem command systems controlling the level of activity of the CPGs and the speed of locomotion. The forebrain and in particular the basal ganglia are involved in determining which motor programs should be recruited at a given point of time and can both initiate and stop locomotor activity. The propulsive control system needs to be integrated with the postural control system to maintain body orientation. Moreover, the locomotor movements need to be steered so that the subject approaches the goal of the locomotor episode, or avoids colliding with elements in the environment or simply escapes at high speed. These different aspects will all be covered in the review.


Assuntos
Sistema Nervoso Central/fisiologia , Locomoção , Vertebrados/fisiologia , Animais , Gânglios da Base/fisiologia , Evolução Biológica , Cerebelo/fisiologia , Humanos , Lampreias/genética , Lampreias/fisiologia , Camundongos , Medula Espinal/fisiologia , Vertebrados/genética , Peixe-Zebra/genética , Peixe-Zebra/fisiologia
3.
PLoS One ; 14(12): e0227057, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31877192

RESUMO

Posterior root-muscle (PRM) reflexes are short-latency spinal reflexes evoked by epidural or transcutaneous spinal cord stimulation (SCS) in clinical and physiological studies. PRM reflexes share key physiological characteristics with the H reflex elicited by electrical stimulation of large-diameter muscle spindle afferents in the tibial nerve. Here, we compared the H reflex and the PRM reflex of soleus in response to transcutaneous stimulation by studying their recovery cycles in ten neurologically intact volunteers and ten individuals with traumatic, chronic spinal cord injury (SCI). The recovery cycles of the reflexes, i.e., the time course of their excitability changes, were assessed by paired pulses with conditioning-test intervals of 20-5000 ms. Between the subject groups, no statistical difference was found for the recovery cycles of the H reflexes, yet those of the PRM reflexes differed significantly, with a striking suppression in the intact group. When comparing the reflex types, they did not differ in the SCI group, while the PRM reflexes were more strongly depressed in the intact group for durations characteristic for presynaptic inhibition. These differences may arise from the concomitant stimulation of several posterior roots containing afferent fibers of various lower extremity nerves by transcutaneous SCS, producing multi-source heteronymous presynaptic inhibition, and the collective dysfunction of inhibitory mechanisms after SCI contributing to spasticity. PRM-reflex recovery cycles additionally obtained for bilateral rectus femoris, biceps femoris, tibialis anterior, and soleus all demonstrated a stronger suppression in the intact group. Within both subject groups, the thigh muscles showed a stronger recovery than the lower leg muscles, which may reflect a characteristic difference in motor control of diverse muscles. Based on the substantial difference between intact and SCI individuals, PRM-reflex depression tested with paired pulses could become a sensitive measure for spasticity and motor recovery.


Assuntos
Reflexo H , Músculo Esquelético/fisiopatologia , Traumatismos da Medula Espinal/fisiopatologia , Traumatismos da Medula Espinal/terapia , Estimulação da Medula Espinal , Adulto , Feminino , Humanos , Masculino , Músculo Esquelético/fisiologia , Reflexo , Medula Espinal/fisiologia , Medula Espinal/fisiopatologia , Estimulação da Medula Espinal/métodos , Adulto Jovem
4.
Int Rev Neurobiol ; 147: 199-217, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31607355

RESUMO

Body-weight-supported locomotor training is an activity-based therapy used frequently to train individuals with spinal cord injury (SCI) for restoring walking ability. Locomotor training after SCI is developed on the basic scientific findings of activity-dependent neuroplasticity. Based on the research from animal SCI models, there exists a spinal neural networks for locomotion which can be reactivated by intense repetitive locomotor training. Notably, the effectiveness of locomotor training depends largely on the severity of injury and time after injury. Locomotor training, using body-weight-supported walking overground or on a treadmill, with assistance manually or robotically, with a variety of training intensity and training programs, has been shown to elicit improvements in locomotor function for incomplete SCI individuals. For chronic and motor complete SCI, other interventions with proven effectiveness such as epidural stimulation might be applied in addition to locomotor training to improve the chance of locomotor recovery. In this chapter, we review the factors that influence the functional outcomes of locomotor training. We also summarize the circuitry, cellular and molecular levels of mechanisms underlying the positive role of locomotor training in inducing neuroplasticity and functional recovery following SCI.


Assuntos
Locomoção/fisiologia , Recuperação de Função Fisiológica/fisiologia , Traumatismos da Medula Espinal/fisiopatologia , Traumatismos da Medula Espinal/terapia , Medula Espinal/fisiologia , Animais , Humanos
5.
Turk Neurosurg ; 29(6): 909-914, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31573062

RESUMO

AIM: To demonstrate the value of special intraoperative neuromonitoring techniques for cauda equina and conus medullaris tumors (CECMT) by describing standard methods used at our center. MATERIAL AND METHODS: Neurophysiological records were retrospectively reviewed for 16 patients (eight females and eight males; age range: 27â€"60 years) who underwent surgery for CECMT at our department between 2016 and 2018. RESULTS: Motor and/or sensorial deficits were preoperatively identified in 10 patients; no patients had bladder or sexual dysfunction. Motor evoked potential (MEP) loss occurred in seven patients with full or partial recovery. No changes were seen in pudendal somatosensory evoked potential (SEP) or bulbocavernosus reflex (BCR), and morphological deterioration and amplitude loss of tibial SEPs were present in four patients. Postoperatively, no new neurological deficits and/or bladder and sexual dysfunction were present. CONCLUSION: Pudendal SEP and BCR are useful tests for monitoring CECMT surgeries. BCR is an easily obtainable modality for preserving sacral functions and recommended as a primary monitoring modality in conjunction with traditional neurophysiological techniques during CECMT surgery.


Assuntos
Cauda Equina/fisiologia , Cauda Equina/cirurgia , Monitorização Neurofisiológica Intraoperatória/métodos , Neoplasias da Medula Espinal/cirurgia , Medula Espinal/fisiologia , Medula Espinal/cirurgia , Adulto , Cauda Equina/diagnóstico por imagem , Potencial Evocado Motor/fisiologia , Potenciais Somatossensoriais Evocados/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Medula Espinal/diagnóstico por imagem , Neoplasias da Medula Espinal/diagnóstico por imagem
6.
PLoS Biol ; 17(9): e3000447, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31513565

RESUMO

In the mouse spinal cord, V1 interneurons are a heterogeneous population of inhibitory spinal interneurons that have been implicated in regulating the frequency of the locomotor rhythm and in organizing flexor and extensor alternation. By introducing archaerhodopsin into engrailed-1-positive neurons, we demonstrate that the function of V1 neurons in locomotor-like activity is more complex than previously thought. In the whole cord, V1 hyperpolarization increased the rhythmic synaptic drive to flexor and extensor motoneurons, increased the spiking in each cycle, and slowed the locomotor-like rhythm. In the hemicord, V1 hyperpolarization accelerated the rhythm after an initial period of tonic activity, implying that a subset of V1 neurons are active in the hemicord, which was confirmed by calcium imaging. Hyperpolarizing V1 neurons resulted in an equalization of the duty cycle in flexor and extensors from an asymmetrical pattern in control recordings in which the extensor bursts were longer than the flexor bursts. Our results suggest that V1 interneurons are composed of several subsets with different functional roles. Furthermore, during V1 hyperpolarization, the default state of the locomotor central pattern generator (CPG) is symmetrical, with antagonist motoneurons each firing with an approximately 50% duty cycle. We hypothesize that one function of the V1 population is to set the burst durations of muscles to be appropriate to their biomechanical function and to adapt to the environmental demands, such as changes in locomotor speed.


Assuntos
Geradores de Padrão Central , Células de Renshaw/fisiologia , Medula Espinal/fisiologia , Animais , Animais Recém-Nascidos , Proteínas Arqueais , Proteínas de Homeodomínio/metabolismo , Técnicas In Vitro , Locomoção , Camundongos , Raízes Nervosas Espinhais/fisiologia
7.
Mater Sci Eng C Mater Biol Appl ; 104: 109902, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31500033

RESUMO

OBJECTIVE: This study sought to promote the adhesion, proliferation and differentiation of rat bone marrow mesenchymal stem cells by constructing a neurotrophin-3 (NT-3) sustained-release system cross-linked with an acellular spinal cord scaffold. METHODS: 1-Ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (EDC) chemistry combined with chemical extraction was used to construct an acellular spinal cord scaffold. The decellularization completion was validated. An EDC cross-linking method was used to construct the NT-3 cross-linked acellular spinal scaffold. ELISA was used to verify sustained release of NT-3; the dorsal root ganglion method was used to verify the biological activity of the sustained-release NT-3. DAPI staining was used to confirm the adhesion of the cultured rat bone marrow mesenchymal stem cells (P3) to the NT-3 scaffold, and cell counting kit-8 (CCK-8) analysis was used to verify the cellular proliferation after 24 h and 48 h of culture. Immunohistochemistry was used to confirm the differentiation of the bone marrow cells into neuron-like cells. RESULTS: An NT-3 sustained-release system cross-linked to an acellular spinal cord scaffold was successfully constructed. Sustained-release NT-3 could persist for 35 days and had biological activity for at least 21 days. It could promote the adhesion, proliferation and differentiation of rat bone marrow mesenchymal stem cells. CONCLUSION: As a composite scaffold, an NT-3 sustained-release system cross-linked with an acellular spinal cord scaffold has potential applications for tissue engineering.


Assuntos
Diferenciação Celular/efeitos dos fármacos , Reagentes para Ligações Cruzadas/farmacologia , Células-Tronco Mesenquimais/citologia , Neurotrofina 3/farmacologia , Medula Espinal/fisiologia , Tecidos Suporte/química , Animais , Adesão Celular/efeitos dos fármacos , Contagem de Células , Proliferação de Células/efeitos dos fármacos , Forma Celular/efeitos dos fármacos , Células Cultivadas , Preparações de Ação Retardada/farmacologia , Gânglios Espinais/efeitos dos fármacos , Gânglios Espinais/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Células-Tronco Mesenquimais/efeitos dos fármacos , Ratos Sprague-Dawley , Medula Espinal/efeitos dos fármacos
8.
Neurology ; 93(12): e1205-e1211, 2019 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-31409736

RESUMO

OBJECTIVE: To determine the hemodynamic conditions associated with optimal neurologic improvement in individuals with acute traumatic spinal cord injury (SCI) who had lumbar intrathecal catheters placed to measure CSF pressure (CSFP). METHODS: Ninety-two individuals with acute SCI were enrolled in this multicenter prospective observational clinical trial. We monitored mean arterial pressure (MAP) and CSFP during the first week after injury and assessed neurologic function at baseline and 6 months after injury. We used relative risk iterations to determine transition points at which the likelihood of either improving neurologically or remaining unchanged neurologically was equivalent. These transition points guided our analyses in which we examined the linear relationships between time spent within target hemodynamic ranges (i.e., clinical adherence) and neurologic recovery. RESULTS: Relative risk transition points for CSFP, MAP, and spinal cord perfusion pressure (SCPP) were linearly associated with neurologic improvement and directed the identification of key hemodynamic target ranges. Clinical adherence to the target ranges was positively and linearly related to improved neurologic outcomes. Adherence to SCPP targets, not MAP targets, was the best indicator of improved neurologic recovery, which occurred with SCPP targets of 60 to 65 mm Hg. Failing to maintain the SCPP within the target ranges was an important detrimental factor in neurologic recovery, particularly if the target range is set lower. CONCLUSION: We provide an empirical, data-driven approach to aid institutions in setting hemodynamic management targets that accept the real-life challenges of adherence to specific targets. Our results provide a framework to guide the development of widespread institutional management guidelines for acute traumatic SCI.


Assuntos
Pressão Sanguínea/fisiologia , Pressão do Líquido Cefalorraquidiano/fisiologia , Traumatismos da Medula Espinal/fisiopatologia , Traumatismos da Medula Espinal/terapia , Medula Espinal/irrigação sanguínea , Medula Espinal/fisiologia , Cateterismo/métodos , Vértebras Cervicais/lesões , Gerenciamento Clínico , Feminino , Hemodinâmica/fisiologia , Humanos , Vértebras Lombares/lesões , Estudos Prospectivos , Traumatismos da Medula Espinal/diagnóstico , Vértebras Torácicas/lesões
9.
Nat Commun ; 10(1): 2937, 2019 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-31270315

RESUMO

During the generation of rhythmic movements, most spinal neurons receive an oscillatory synaptic drive. The neuronal architecture underlying this drive is unknown, and the corresponding network size and sparseness have not yet been addressed. If the input originates from a small central pattern generator (CPG) with dense divergent connectivity, it will induce correlated input to all receiving neurons, while sparse convergent wiring will induce a weak correlation, if any. Here, we use pairwise recordings of spinal neurons to measure synaptic correlations and thus infer the wiring architecture qualitatively. A strong correlation on a slow timescale implies functional relatedness and a common source, which will also cause correlation on fast timescale due to shared synaptic connections. However, we consistently find marginal coupling between slow and fast correlations regardless of neuronal identity. This suggests either sparse convergent connectivity or a CPG network with recurrent inhibition that actively decorrelates common input.


Assuntos
Medula Espinal/fisiologia , Animais , Feminino , Cinética , Masculino , Modelos Neurológicos , Neurônios/química , Neurônios/fisiologia , Medula Espinal/química , Sinapses/fisiologia , Transmissão Sináptica , Fatores de Tempo , Tartarugas
10.
Handb Clin Neurol ; 160: 329-344, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31277858

RESUMO

Spinal cord surgery carries the risk of spinal cord or nerve root injury. Neurophysiologic monitoring decreases risk of injury by continuous assessment of spinal cord and nerve root function throughout surgery. Techniques include somatosensory evoked potentials (SEPs), transcranial electrical motor evoked potentials (MEPs), and electromyography (EMG). Baseline neurophysiologic data are obtained prior to incision. Real-time signal changes are identified in time to correct compromised neural function. Such monitoring improves postoperative neurologic functional outcomes. Challenges in neurophysiologic intraoperative monitoring (NIOM) include effects of anesthetics, neuromuscular blockade, hypotension, hypothermia, and preexisting neurological conditions, e.g., neuropathy or myelopathy. Technical factors causing poor quality data must be overcome in the electrically noisy operating room environment. Experienced monitoring teams understand tactics to obtain quality recordings and consider confounding variables before raising alarms when change occurs. Once an alert is raised, surgeons and anesthesiologists respond with a variety of actions, such as raising blood pressure or adjusting retractors. In experienced hands, NIOM significantly reduces postoperative neurological deficits, e.g., 60% reduction in risk of paraplegia and paraparesis. A technologist in the operating room sets up the NIOM procedure. An experienced clinical neurophysiologist supervises the case, either in the operating room or remotely on-line continuously in real time.


Assuntos
Potencial Evocado Motor/fisiologia , Potenciais Somatossensoriais Evocados/fisiologia , Monitorização Intraoperatória/métodos , Medula Espinal/fisiologia , Medula Espinal/cirurgia , Humanos , Monitorização Intraoperatória/normas , Procedimentos Neurocirúrgicos/métodos , Procedimentos Neurocirúrgicos/normas
11.
Handb Clin Neurol ; 160: 407-418, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31277865

RESUMO

The autonomic nervous system has widespread innervation to nearly every organ system in the body. In order to understand the basics of autonomic function, knowledge of the neuroanatomy of the autonomic nervous system is necessary. Frequently considered to control the "fight or flight" and "rest and digest" functions, the autonomic nervous system has an intricate network of connections to finely tune the systemic response to nearly any situation. Although traditionally considered two discrete systems (sympathetic and parasympathetic), the enteric nervous system is now considered a third component of the autonomic nervous system. This chapter reviews the background of the neuroanatomical distribution of the autonomic nervous system in order to facilitate understanding the basics of autonomic function.


Assuntos
Sistema Nervoso Autônomo/fisiologia , Encéfalo/fisiologia , Medula Espinal/fisiologia , Animais , Doenças do Sistema Nervoso Autônomo/diagnóstico , Doenças do Sistema Nervoso Autônomo/fisiopatologia , Sistema Nervoso Entérico/fisiologia , Frequência Cardíaca/fisiologia , Humanos
12.
Braz J Med Biol Res ; 52(7): e8429, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31314852

RESUMO

The present study aimed to analyze age-related changes to motor coordination, balance, spinal cord oxidative biomarkers in 3-, 6-, 18-, 24-, and 30-month-old rats. The effects of low-intensity exercise on these parameters were also analyzed in 6-, 18-, and 24-month-old rats. Body weight, blood glucose, total cholesterol, and high-density lipoprotein (HDL) cholesterol were assessed for all rats. The soleus muscle weight/body weight ratio was used to estimate skeletal muscle mass loss. Body weight increased until 24 months; only 30-month-old rats exhibited decreased blood glucose and increased total cholesterol and HDL cholesterol. The soleus muscle weight/body weight ratio increased until 18 months, followed by a small decrease in old rats. Exercise did not change any of these parameters. Stride length and step length increased from adult to middle age, but decreased at old age. Stride width increased while the sciatic functional index decreased in old rats. Performance in the balance beam test declined with age. While gait did not change, balance improved after exercise. Aging increased superoxide anion generation, hydrogen peroxide levels, total antioxidant capacity, and superoxide dismutase activity while total thiol decreased and lipid hydroperoxides did not change. Exercise did not significantly change this scenario. Thus, aging increased oxidative stress in the spinal cord, which may be associated with age-induced changes in gait and balance. Regular low-intensity exercise is a good alternative for improving age-induced changes in balance, while beneficial effects on gait and spinal cord oxidative biomarkers cannot be ruled out because of the small number of rats investigated (n=5 or 6/group).


Assuntos
Fatores Etários , Biomarcadores/sangue , Marcha/fisiologia , Estresse Oxidativo/fisiologia , Condicionamento Físico Animal/fisiologia , Equilíbrio Postural/fisiologia , Medula Espinal/fisiologia , Animais , Biomarcadores/metabolismo , Glicemia/análise , Peso Corporal/fisiologia , Colesterol/sangue , Lipoproteínas HDL/sangue , Masculino , Ratos , Ratos Wistar , Medula Espinal/metabolismo
14.
J Integr Neurosci ; 18(2): 163-172, 2019 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-31321957

RESUMO

In this paper, the modulation of ascending commissural interneurons by N-methyl-D-aspartate was investigated in neonatal rats by using retrograde labeling and whole-cell patch clamp. Data shows these interneurons can be divided into three types (single spike, phasic, and tonic) based on their firing patterns. A hyperpolarization-activated nonselective cation current and persistent inward current are expressed in these interneurons. The parameters studied (n = 48) include: resting membrane potential (-59.2 ± 0.8 mV), input resistance (964.4 ± 49.3 MΩ), voltage threshold (-39.5 ± 0.6 mV), rheobase (13.5 ± 0.7 pA), action potential height (55.6 ± 2.2 mV), action potential half-width (2.8 ± 0.1 ms), afterhyperpolarization magnitude (16.1 ± 1.2 mV) and half-decay (217.9 ± 10.7 ms). 10 µM N-methyl-D-aspartate increases excitability of ascending commissural interneurons by depolarizing the membrane potential, hyperpolarizing voltage threshold, reducing rheobase, and shifting the frequency-current relationship to the left. N-methyl-Daspartate enhances persistent inward currents but reduces hyperpolarization-activated nonselective cation currents. This research uncovers unique ionic and intrinsic properties of ascending commissural interneurons which can be modulated by major excitatory neurotransmitters such as N-methyl-D-aspartate to potentially facilitate left-right alternation during locomotion.


Assuntos
Interneurônios Comissurais/fisiologia , Potenciais da Membrana , N-Metilaspartato/fisiologia , Medula Espinal/fisiologia , Potenciais de Ação/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Interneurônios Comissurais/citologia , Interneurônios Comissurais/efeitos dos fármacos , Agonistas de Aminoácidos Excitatórios/administração & dosagem , Potenciais da Membrana/efeitos dos fármacos , N-Metilaspartato/administração & dosagem , Ratos Wistar , Medula Espinal/citologia , Medula Espinal/efeitos dos fármacos
15.
Clin Nucl Med ; 44(10): 804-805, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31306210

RESUMO

Falx cerebri ossification is an incidental finding. Mostly it is easy to diagnose, but can be challenging in few cases, and should be distinguished from calcified meningioma, hematoma, and meningeal infiltration. We report a case of a 46-year-old woman with breast cancer complaining of back pain. F-NaF PET/CT images show focal increase uptake at facet joints of L5/S1 vertebrae and both knees joints, suggesting degenerative disease. There is normal variant F-NaF uptake noted in the ossification at the falx cerebri. Recognition of normal and abnormal extraosseous F-NaF uptake is important for correct interpretation to avoid unnecessary further investigations.


Assuntos
Radioisótopos de Flúor , Osteogênese , Fluoreto de Sódio/metabolismo , Medula Espinal/fisiologia , Transporte Biológico , Feminino , Humanos , Achados Incidentais , Pessoa de Meia-Idade , Tomografia Computadorizada com Tomografia por Emissão de Pósitrons , Medula Espinal/diagnóstico por imagem , Medula Espinal/metabolismo
16.
Exp Brain Res ; 237(9): 2319-2329, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31286172

RESUMO

Arm cycling causes suppression of soleus (SOL) Hoffmann (H-) reflex that outlasts the activity period. Arm cycling presumably activates propriospinal networks that modulate Ia presynaptic inhibition. Interlimb pathways are thought to relate to the control of quadrupedal locomotion, allowing for smooth, coordinated movement of the arms and legs. We examined whether the number of active limb pairs affects the amount and duration of activity-dependent plasticity of the SOL H-reflex. On separate days, 14 participants completed 4 randomly ordered 30 min experimental sessions: (1) quiet sitting (CTRL); (2) arm cycling (ARM); (3) leg cycling (LEG); and (4) arm and leg cycling (A&L) on an ergometer. SOL H-reflex and M-wave were evoked via electrical stimulation of the tibial nerve. M-wave and H-reflex recruitment curves were recorded, while the participants sat quietly prior to, 10 and 20 min into, immediately after, and at 2.5, 5, 7.5, 10, 15, 20, 25, and 30 min after each experimental session. Normalized maximal H-reflexes were unchanged in CTRL, but were suppressed by > 30% during the ARM, LEG, and A&L. H-reflex suppression outlasted activity duration for ARM (≤ 2.5 mins), LEG (≤ 5 mins), and A&L (≤ 30 mins). The duration of reflex suppression after A&L was greater than the algebraic summation of ARM and LEG. This non-linear summation suggests that using the arms and legs simultaneously-as in typical locomotor synergies-amplifies networks responsible for the short-term plasticity of lumbar spinal cord excitability. Enhanced activity of spinal networks may have important implications for the implementation of locomotor training for targeted rehabilitation.


Assuntos
Braço/fisiologia , Reflexo H/fisiologia , Perna (Membro)/fisiologia , Atividade Motora/fisiologia , Músculo Esquelético/fisiologia , Plasticidade Neuronal/fisiologia , Medula Espinal/fisiologia , Adulto , Estimulação Elétrica , Feminino , Humanos , Masculino , Rede Nervosa/fisiologia , Adulto Jovem
18.
Dokl Biol Sci ; 485(1): 27-29, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31197588

RESUMO

Changes in the blood flow in the shin skin were observed by laser Doppler flowmetry after transcutaneous electrical spinal cord stimulation (TSCS) by subthreshold bipolar pulses with a frequency of 30 Hz in 12 healthy subjects. It was found that TSCS in the area of the T11 and L1 vertebrae led to a significant increase in skin blood flow. The microcirculation rate increased by more than 85% relative to the baseline at a stimulus intensity of 90% of the motor threshold. Cutaneous blood flow activization by TSCS is implemented mainly through the antidromic stimulation of sensory nerve fibers. Nitric oxide (NO) is an important mediator that contributes to vasodilation and increase in cutaneous blood flow upon TSCS. NO is predominantly of endothelial origin.


Assuntos
Fluxo Sanguíneo Regional , Pele/irrigação sanguínea , Medula Espinal/fisiologia , Adulto , Feminino , Humanos , Fluxometria por Laser-Doppler , Masculino , Estimulação Elétrica Nervosa Transcutânea
19.
Exp Brain Res ; 237(9): 2239-2254, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31243484

RESUMO

The purpose of this study was to assess corticospinal excitability of soleus (SOL) and tibialis anterior (TA) at a segmental level during passive ankle movement. Four experimental components were performed to assess the effects of passive ankle movement and muscle length on corticospinal excitability (MEP/Mmax) at different muscle lengths, subcortical excitability at the level of lumbar spinal segments (LEP/Mmax), intracortical inhibition (SICI) and facilitation (ICF), and H-reflex in SOL and TA. In addition, the degree of fascicle length changes between SOL and TA was assessed in a subpopulation during passive ankle movement. Fascicles shortened and lengthened with joint movement during passive shortening and lengthening of SOL and TA to a similar degree (p < 0.001). Resting motor threshold was greater in SOL compared to TA (p ≤ 0.014). MEP/Mmax was facilitated in TA during passive shortening relative to the static position (p ≤ 0.023) and passive lengthening (p ≤ 0.001), but remained similar during passive ankle movement in SOL (p ≥ 0.497), regardless of muscle length at the point of stimulus (p = 0.922). LEP/Mmax (SOL: p = 0.075, TA: p = 0.071), SICI (SOL: p = 0.427, TA: p = 0.540), and ICF (SOL: p = 0.177, TA: p = 0.777) remained similar during passive ankle movement. H-reflex was not different across conditions in TA (p = 0.258), but was reduced during passive lengthening compared to shortening in SOL (p = 0.048). These results suggest a differential modulation of corticospinal excitability between plantar and dorsiflexors during passive movement. The corticospinal behaviour observed might be mediated by an increase in corticospinal drive as a result of reduced afferent input during muscle shortening and appears to be flexor-biased.


Assuntos
Tornozelo/fisiologia , Potencial Evocado Motor/fisiologia , Reflexo H/fisiologia , Movimento/fisiologia , Músculo Esquelético/fisiologia , Medula Espinal/fisiologia , Nervo Tibial/fisiologia , Adulto , Vias Aferentes/fisiologia , Estimulação Elétrica , Eletromiografia , Feminino , Humanos , Vértebras Lombares , Masculino , Estimulação Magnética Transcraniana , Adulto Jovem
20.
Med Biol Eng Comput ; 57(9): 1843-1860, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31209711

RESUMO

This article shows the design of a robust second-order sliding mode controller to solve the trajectory tracking problem of an active orthosis for assisting back physiotherapies. The orthosis was designed in agreement with morphological dimensions and its articulations distribution followed the same designing rules. The orthosis has six articulated arms attached to an articulated column. The orthosis was fully instrumented with actuators and position sensors at each articulation. The controller implemented a class of hybrid/position controller depending on the relative force exerted by the patient and the orthosis movement. The position information provided by each articulation was supplied to a distributed super-twisting differentiator to recover the corresponding angular velocity. A set of twisting controllers was implemented to regulate the position of the robot in agreement to predefined reference trajectories. Reference trajectories were obtained from a biomechanical-based analysis. The hybrid tracking control problem solved the automation of the assisted therapy to the patient, including the force feedback. The performance of the orthosis was tested with different dummy bodies with different resistance. The robust output feedback controller successfully tracked the reference trajectories despite the material of the dummy used during the testing. The orthosis was evaluated with two volunteers using a simple reference trajectory. Graphical Abstract General structure of the active back assisted orthosis.


Assuntos
Aparelhos Ortopédicos , Modalidades de Fisioterapia/instrumentação , Medula Espinal/fisiopatologia , Simulação por Computador , Desenho de Equipamento , Retroalimentação , Humanos , Modelos Teóricos , Robótica/instrumentação , Robótica/métodos , Software , Medula Espinal/fisiologia
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