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The rhythmic activity of locomotion is most frequently modeled as a periodic oscillation coordinated by a spinal Central Pattern Generator (CPG) controlling reciprocal activation of flexor and extensor muscles. Expression of locomotion errors in the form of spontaneous deletions in the motor output has been critical in formulating models of CPG network structure governing locomotion in mammals (Lafreniere-Roula et al 2005, Duysens 2006). Deletions are defined as the disappearance of either antagonist or agonist muscles’ activity along with the simultaneous tonic/rhythmic activity of the corresponding agonist or antagonist muscles. The formulation of a two-layer model of the CPG (Rhythm Generator (RG) layer & Pattern Formation (PF) layer) by Rybak et al (2006) stems from observations of such deletions in the fictive locomotion of the decerebrated cat. The RG functions as a clock controlling the temporal activity of the PF layer which controls the firing pattern of motor neuron pools that activate muscles. The deletion episodes are said to be “resetting” if the EMG activity after the deletion does not return after an integer value of the pre-deletion average period. If the motoneuron activity returns in phase with the pre-deletion “clock”, the deletion period is considered to be “non-resetting”. Multiunit Activity (MUA) recorded from a spinalised air-stepping cat was analyzed against its corresponding EMG activity to investigate the role of MUA in rhythmogenicity, specifically whether or not MUA activity may represent the RG layer of the Central Pattern Generator (CPG) model. This hypothesis would predict that MUA activity should be disrupted in phase or amplitude when and only when deletions episodes are re-setting.. Alternatively, MUA activity may reflect PF layer activity. In this case MUA activity should be disrupted in phase or amplitude during each of the deletions episodes. MUA’s spatio-temporal characteristics were compared to that of the EMG activity during the deletion periods for analysis. From the analysis performed, there was a significant proportion (average more than 25%) of the MUA (collected from the lumbar region of the spinal cord of spinalized cat) that were disrupted in phase or amplitude during non-resetting deletions or undisrupted during resetting episodes, indicating that MUA activity is unlikely to represent the RG layer activity during . In addition, MUA oscillation during the period of deletions was unchanged (amplitude or phase) for more than 25% of the deletion episodes, ruling out the possibility that MUA represents the activity of the PF layer. So although MUA has been found to be highly synchronized throughout the lumbar extent during locomotor activity, it does not appear to act as a “clocking” mechanism for the locomotor rhythm. / Bioengineering

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25283号 / 工博第5242号 / 新制||工||1998(附属図書館) / 京都大学大学院工学研究科航空宇宙工学専攻 / (主査)教授 藤本 健治, 准教授 丸田 一郎, 教授 大塚 敏之, 教授 青井 伸也(大阪大学) / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Résumé : Suite à une lésion de la moelle épinière, divers comportements moteurs invalidants, tels des spasmes peuvent apparaître. Les traitements actuels pour la spasticité causent divers effets secondaires, dont une réduction de la capacité locomotrice des patients. La recherche de traitements non invasifs et non pharmacologiques permettant de réduire la spasticité sans affecter la récupération fonctionnelle du patient s’avère donc un enjeu prioritaire. Par ailleurs, une réduction des spasmes rythmiques peut être observée lorsque la peau lombosacrée est pincée. Ce potentiel inhibiteur d’une stimulation cutanée tonique est également perçu chez l’animal comme le lapin et le chat suite à une perte des voies supraspinales. Par contre, bien que ce type de stimulation semble efficace pour réduire la spasticité, son effet sur la capacité locomotrice n’a toujours pas été évalué. L’objectif du projet était de déterminer l’effet d’un pincement de la peau à divers niveaux lombaires sur la locomotion du chat ayant une lésion de la moelle épinière. Six chats implantés chroniquement pour l’électromyographie (EMG) ont subi une lésion complète de la moelle épinière au niveau thoracique et ont été entraînés sur tapis roulant pour récupérer une fonction locomotrice des pattes postérieures. L’effet d’une stimulation de 6 sites cutanés sur la ligne médiane au niveau des vertèbres lombaires L2 à L7 a été évalué lors de marche à 0.4 m/s via des analyses cinématiques et EMG. Les résultats obtenus démontrent que la zone cutanée perturbant le plus l’activité locomotrice se trouve sur la ligne médiane au niveau lombaire L4. À ce niveau, une diminution de l’activité des extenseurs et des fléchisseurs est perçue au niveau de l’EMG. De plus, des modifications du patron locomoteur comme un positionnement plus caudal de la patte lors de son contact et de son décollage sont également visibles, tout comme une perte du support de poids (force de réaction au sol). La coordination spatiale entre les pattes postérieures est également perturbée. Ces résultats suggèrent que bien que la stimulation cutanée puisse être une alternative intéressante pour le traitement non pharmacologique de la spasticité, celle-ci altère la capacité locomotrice. || Abstract : After a spinal cord injury, multiple abnormal motor activities can occur, such as rhythmic spasms. These activities can be invalidating and are treated with different drugs that cause various side effects, including a reduction of locomotor ability in patients. Therefore, there is a need for novel non-invasive and non-pharmacological treatments for spasticity that will not affect the functional recovery of patients. A reduction of rhythmic spasms can be observed when the lumbosacral skin is pinched in a spinal cord-injured patient. This inhibition of rhythmic activity by a tonic cutaneous stimulation is also present in cats and rabbits after the loss of supraspinal input. Although this stimulation seems effective to reduce spasticity, its effects on real locomotion have not been evaluated. The goal of this project was to determine the effect of stimulating the skin at different lumbar levels on hindlimb locomotion of the spinal cord-transected (spinalized) cat. Six cats chronically implanted for electromyography (EMG) recording were spinalized at low thoracic levels and trained to recover hindlimb locomotion on a treadmill. The effect of stimulating the skin over the midline of lumbar vertebrae was evaluated during locomotion at 0.4 m/s and compared to control trials (without stimulation) with kinematic, kinetic and EMG analyses. Stimulating the lumbar skin disrupted hindlimb locomotion, with the largest effects observed at mid-lumbar levels. Cutaneous stimulation reduced extensor and flexor EMG activity. Moreover, position of the paw at contact and lift-off was more caudal and there was a loss of body weight support with cutaneous stimulation. Spatial coordination between the hindlimb was also perturbed by the cutaneous stimulation. Thus, results suggest that despite the fact that cutaneous stimulation appears to be an interesting approach to diminish rhythmic spasms in spinal cord-injured patients, it disrupts spinal-mediated locomotor capacity.

Introdução: A Locomoção tem como uma das características básicas a ritmicidade. Entre os mecanismos que envolvem seu controle destaca-se o conceito de um gerador de padrão central (GPC) capaz de gerar atividades neurais e musculares rítmicas. A técnica de treino locomotor com suspensão de peso na esteira (TLSP) utiliza esse conceito e emerge como uma estratégia terapêutica efetiva após a lesão medular (LM) em humanos em função do alto nível de automatismo do sistema nervoso, podendo ser esperadas diferentes respostas em lesões completas e incompletas. Portanto, uma análise detalhada das respostas biomecânicas obtidas durante o TLSP pode servir como base para compreensão do controle neural da locomoção humana. Objetivos: Caracterizar, a partir de parâmetros biomecânicos, a marcha com suspensão parcial de peso e assistência manual em indivíduos com lesões medulares completas e incompletas. Método: 40 indivíduos (20 com LM e 20 sem lesão) foram divididos em quatro grupos: Lesão Medular ASIA A (GLA), Lesão Medular ASIA B (GLB), Lesão Medular ASIA C e D (GLC) e Grupo Controle (GC) composto por sujeitos sem lesão. Durante o TLSP, ambos os grupos foram submetidos ao mesmo protocolo, com suspensão do peso corporal, duração total do treino e velocidades pré-definidas. Foram coletados dados de eletromiografia de superfície e a análise cinemática foi realizada por meio de 7 centrais inerciais. As análises foram realizadas por meio de análise de variância múltipla (MANOVA) Resultados: Em relação às variáveis cinemáticas o GC apresentou menor tempo de apoio em relação ao GLA não havendo diferenças entre os outros grupos com lesão medular. Quanto à ativação muscular o GLA e GLB apresentaram maior atividade de músculos proximais com co-contrações, GLC atividade proximal similar à GLA, GLB e distal similar ao GC que apresentou níveis mais baixos de atividade muscular com maior atividade distal em relação a proximal. Para o momento do pico de atividade, o GC apresentou momento antecipado para músculos proximais, atrasado para músculos distais em relação aos grupos com LM. Conclusão: Quando comparados ao GC, os grupos com LM apresentaram maiores amplitudes de sinal eletromiográfico, provavelmente pelo fato de o GC realizar a tarefa de forma mais eficiente com menor demanda de ativação muscular. Não foi possível reconhecer padrões rítmicos de ativação nos grupos com LM / Introduction: The locomotion has a characteristic the rhythmicity. Concerning the understanding of the mechanisms involving its control, the concept of a central pattern generator (GPC) capable of generating neural and muscular rhythmic activities stands out. The body weight support treadmill training (BWSTT) technique uses this concept and emerges as an effective therapeutic strategy after spinal cord injury (LM) in humans due to the high level of automatism of the nervous system, and different responses can be expected in complete and incomplete injuries. Therefore, a detailed analysis of the biomechanical responses obtained during BWSTT may serve as a basis for understanding the neural control of human locomotion. Objectives: To characterize, from biomechanical parameters, treadmill gait with body weight support in individuals with complete and incomplete spinal cord injury. Method: 40 individuals (20 with LM and 20 without lesion) were divided into four groups: ASIA A (GLA), ASIA B (GLB), ASIA C and D (GLC) and Control Group (GC) composed of subjects without injury. During BWSTT, both groups were submitted to the same protocol, with pre-defined body weight suspension, total training duration and speeds. Surface electromyography data were collected and kinematic analysis was performed by means of 7 inertial power plants. The analyzes were performed through multiple variance analysis (MANOVA). Results: In the kinematic variables, the CG presented less support time in relation to the GLA and there were no differences between the other groups with spinal cord injury. As for muscle activation, GLA and GLB presented higher activity of proximal muscles with co-contractions, GLC presented similar proximal activity similar to GLA, GLB and distal similar to GC, which presented lower levels of muscular activity with greater distal activity in relation to proximal muscles. For the moment of peak activity, the GC presented early moment for proximal muscles, delayed to distal muscles in relation to the groups with LM. Conclusion: When compared to CG, the groups with LM presented higher amplitudes of electromyographic signal, probably because the CG performed the task more efficiently with less demand for muscle activation. It was not possible to recognize rhythmic patterns of activation in the LM groups

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