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Animals control locomotion through unpredictable and complex habitats using a single locomotor control system. Because of the disparate physical mechanics of different environments, behavioural plasticity, based on the complex interplay of sensory feedback and environmental constraints, is likely essential for animals moving across environments. However, few studies have investigated neuromuscular control across different environments. To fill this gap, I make use of Polypterus senegalus to address four primary objectives: (1) to explore the extent of neuromuscular plasticity across environmental gradients (viscosity and water depth), (2) to generate and test hypotheses about paramount signals for this neuromuscular plasticity, (3) to determine the neuromuscular underpinnings of locomotor transitions, and (4) to determine the neuromuscular control of developmental behavioural plasticity in novel environments. I measured the kinematic and muscle activity response of P. senegalus to gradual changes in environment forces using gradients of water viscosity and water depth. I then used a semi-intact preparation to investigate the existence and role of the mesencephalic locomotor region, a brain region that controls locomotor speed and mode in other species, for neuromuscular control in P. senegalus. Finally, I used chronic terrestrial acclimation and exercise to determine the neuromuscular underpinnings of behavioural and morphological plasticity previously seen in P. senegalus reared in a terrestrial environment. I found that in high viscosity environments, P. senegalus maintain routine swimming speed using a swimming-like muscle activity pattern with increased effort in the posterior body and the pectoral fin to generate exaggerated swimming kinematics. These results suggest that sensory feedback is essential to accommodating this novel environment. I then demonstrated that axial red muscle always carried an anterior-to-posterior wave of muscle activity in a series of discrete water depths across the aquatic-terrestrial transition. Thus, discrete changes in axial kinematics and pectoral fin coordination across this transtion are likely the result of sensory feedback and mechanical constraints of the environment. I then performed the first experiments searching for the mesencephalic locomotor region in P. senegalus and demonstrated the presence of a putative mesencephalic locomotor region that controls the frequency of swimming-like movements but does not appear to control pectoral fin movements or the transition to walking. Finally, I exposed P. senegalus to chronic terrestrial acclimation and exercise. My results suggested that while both terrestrial acclimation and exercise generate behavioural plasticity, the former results in a larger plastic repsonse. Subtle changes in the duration and timing of pectoral fin muscle activity helped reduce friction between the body and pectoral fin and the substrate below, potentially resulting in the more “effective” walking gait developed by terrestrial acclimated fish. My thesis therefore sheds light on the essential interplay of sensory feedback and mechanical constraint for generating behavioural plasticity on acute and chronic timescales, highlights the potential value of such plasticity for organismal performance and evolution, and develops study systems and experimental frameworks for further investigating the nature of plastic locomotor control in amphibious fish.

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.

Esta dissertação parte da premissa de que o desalinhamento dos arcos plantares estão associados ao mal funcionamento do pé e a subseqüentes desequilíbrios mecânicos gerados por compensações na cadeia cinética e articulações adjacentes. A bandagem plantar é uma das técnicas comumente utilizadas no tratamento e prevenção de lesões decorrentes destes desalinhamentos; no entanto, sua eficácia no controle postural ainda é incerta. Nossas hipóteses são: (i) que sujeitos com arco rebaixado apresentariam déficits do controle postural que se acentuariam em condições de perturbação sensorial, e (ii) que a bandagem aplicada no médio-­pé para melhorar a acuidade sensorial traria benefícios para o controle postural destes sujeitos, principalmente nas condições de perturbação. Assim, apresentaremos nesta dissertação dois estudos, um para investigar as alterações no controle postural de indivíduos com rebaixamento do arco plantar (estudo 1), e outro para investigar as consequências da utilização bandagem plantar nestes indivíduos (estudo 2). Para ambos os estudos, avaliamos a velocidade média e o root mean square da trajetória do centro de pressão durante a manutenção da postura quasi-­-estática em quatro condições de perturbação sensorial: (1) plataforma fixa, olhos abertos; (2) plataforma fixa, olhos fechados; (3) plataforma móvel, olhos abertos; e (4) plataforma móvel, olhos fechados. No estudo 1, 24 mulheres com arcos normais foram comparadas a 13 mulheres com arco rebaixado. No estudo 2, a comparação foi feita entre as condições sem e com a bandagem plantar para as 13 mulheres com arco rebaixado. Os resultados indicam que mulheres com rebaixamento do arco oscilam menos e mais lentamente que mulheres com arco normal, em particular na condição de maior perturbação sensorial, o que pode representar uma resposta pior, ou mais lenta de um sistema com desequilíbrios mecânicos decorrentes de um pé pouco funcional. Já a utilização da bandagem plantar resultou em aumento da oscilação do centro de pressão para a maioria das condições de perturbação sensorial, principalmente na direção médio-­-lateral, o que pode ser explicado por uma dificuldade dos sujeitos em se ajustar a uma nova postura, ou indicar um ganho de confiança e um melhor funcionamento do pé, traduzido pelo aumento da utilização dos ajustes posturais. / This dissertation is based on the premise that misalignment of plantar arches are associated to poor foot function and to subsequent mechanical compensations in the kinetic chain and adjacent joints. Foot taping is a commonly used technique in the treatment and prevention of injuries caused by these misalignments; however, its efficacy on postural control is still uncertain. Our hypotheses are: (i) subjects with low plantar arch would present postural control deficits, detectable by center of pressure sway measurement, that would be worsened in conditions of sensory perturbation, and (ii) foot taping, applied on midfoot with the intention to improve the cutaneous sensorial acuity, would bring benefits to the postural control of these subjects, especially under conditions of sensory perturbation. Thus, two studies will be presented: the first meant to investigate postural control alterations in individuals with low plantar arch (study 1), and the second, to investigate the effects of foot taping use in these subjects (study 2). For both studies, the mean velocity and root mean square of center of pressure trajectory were assessed during the maintenance of quasi-static stance in four conditions of sensory perturbations: (1) fixed support, eyes opened; (2) fixed support, eyes closed; (3) moving support, eyes opened, and (4) moving support, eyes closed. In study 1, 24 women with normal plantar arch were compared to 13 with low plantar arch. For study 2, the same 13 low arched subjects were assessed with and without foot taping. Results indicate that women with low plantar arch have less and slower center of pressure sway, particularly in the condition of highest sensory perturbation level, which may indicate a worsened, or slower, response of a mechanically altered system. When foot taping was applied to the low arched individuals, a higher and faster center of pressure sway was observed in most of the sensory perturbation conditions, especially in the medio-lateral direction. This could be explained either by a difficulty for the subjects to adapt to a new imposed postural condition, or by a gain in confidence while using the taping, reflected by the increase in postural adjustments.

Introdução: O objetivo desse estudo foi investigar o efeito da instrução para ativação consciente da musculatura abdominal sobre a atividade dos músculos escapulotorácicos durante exercícios de ombro. Métodos: Foram avaliados sessenta e cinco indivíduos assintomáticos do sexo feminino e masculino (média de idade de 23,5 ± 3 anos). Cinco exercícios enfocados no músculo serrátil anterior foram avaliados antes e depois do comando verbal e do estímulo táctil para ativação da musculatura abdominal. Foi utilizado o teste ANOVA para medidas repetitivas com teste Bonferroni post-hoc para comparar os valores eletromiográficos normalizados. Tamanhos de efeito com magnitudes moderadas e grandes foram considerados indicadores de significância em termos práticos. Resultados: Ativação consciente dos músculos abdominais resultou em um incremento significativo (p<,05) na atividade eletromiográfica dos músculos serrátil anterior e trapézio em suas fibras descendente, transversa e ascendente durante os exercícios dinâmicos (Wall Slide, Wall Press e Knee Push). A instrução aumentou a atividade eletromiográfica somente do músculo serrátil anterior durante os exercícios isométricos (Inferior Glide e Isometric Low Row). Conclusão: Ativação consciente dos músculos abdominais incentivada por comando verbal e estímulo tátil foi efetiva para incrementar a ativação dos músculos escapulotorácicos durante exercícios de ombro, principalmente para o músculo serrátil anterior com um tamanho de efeito de moderado a grande. / Introduction: The purpose of this study was to investigate the effect of the instruction for conscious contraction of the abdominal muscles on the scapulothoracic muscles activation during shoulder exercises. Methods: Sixty healthy male and female subjects (mean age 23.5 ± 3 years) volunteered for this study. Five exercises focusing on the serratus anterior muscle were assessed before and after standardized verbal, and tactile feedback applied to encourage abdominal muscle contraction. Repeated measures ANOVA and Bonferroni post-hoc test were used to compare normalized EMG amplitudes. Moderate and large magnitudes of effect size were considered indicators of the practical significance of our findings. Results: Conscious contraction of the abdominal muscles resulted in significant increase (p<.05) in serratus anterior, upper, middle and lower trapezius EMG amplitude, during dynamic exercises (Wall Slide, Wall Press, and Knee Push). Instruction increased EMG amplitude only for serratus anterior muscle during isometric exercises (Inferior Glide and Isometric Low Row). Conclusion: Conscious activation of the abdominal muscles, encouraged by verbal and tactile feedback was effective to increase the activation of periscapular muscles during shoulder exercises, in particular, the serratus anterior with large and moderate magnitudes of effect size.

The area of Human-Robot Interaction deals with problems not only related to robots interacting with humans, but also with problems related to humans interacting and controlling robots. This dissertation focuses on the latter and evaluates multi-sensory (vision, hearing, touch, smell) feedback interfaces as a means to improve robot-operator cognition and performance. A set of four empirical studies using both simulated and real robotic systems evaluated a set of multi-sensory feedback interfaces with various levels of complexity. The task scenario for the robot in these studies involved the search for victims in a debris-filled environment after a fictitious catastrophic event (e.g., earthquake) took place. The results show that, if well-designed, multi-sensory feedback interfaces can indeed improve the robot operator data perception and performance. Improvements in operator performance were detected for navigation and search tasks despite minor increases in workload. In fact, some of the multi-sensory interfaces evaluated even led to a reduction in workload. The results also point out that redundant feedback is not always beneficial to the operator. While introducing the concept of operator omni-directional perception, that is, the operator’s capability of perceiving data or events coming from all senses and in all directions, this work explains that feedback redundancy is only beneficial when it enhances the operator omni-directional perception of data relevant to the task at hand. Last, the comprehensive methodology employed and refined over the course of the four studies is suggested as a starting point for the design of future HRI user studies. In summary, this work sheds some light on the benefits and challenges multi-sensory feedback interfaces bring, specifically on teleoperated robotics. It adds to our current understanding of these kinds of interfaces and provides a few insights to assist the continuation of research in the area.

Rhythmic movementssuch as swimming, flying, and walkingare ubiquitous in nature. Intrinsically active neural networks called central pattern generators (CPGs) provide the feedforward signals to actuate these movements, but the preferred movement frequency is often equivalent to the resonant frequency of the musculoskeletal system. Sensory feedback is essential to synchronize the neural and musculoskeletal systems to the mechanical resonant frequency, a phenomenon called resonance tuning. In this dissertation, we use a simple computational model of rhythmic movement to understand how the configuration of sensory feedback affects both the sensitivity of resonance tuning to parameter variation and the resiliency of resonance tuning to perturbation. Although previous studies have shown that resonance tuning is limited to frequencies that are above the intrinsic CPG frequency, we demonstrate that this limitation is only valid with negative feedback and with endogenously bursting CPG neurons. Specifically, we show that with positive feedback, resonance tuning occurs at frequencies that are below the intrinsic CPG frequency. Moreover, when the synaptic connections within the CPG are required for bursting activity, resonance tuning occurs both above and below the intrinsic CPG frequency with negative feedback and does not occur with positive feedback. Using Floquet analysis, we then demonstrate that perturbations decay more quickly when resonance tuning is realized with positive than with negative proportional feedback. Finally, we evaluate how the intrinsic CPG frequency, feedback gain, and mechanical damping affect the stability and range of resonance tuning with negative and positive feedback. Overall, these results indicate that the configuration of sensory feedback dramatically affects both the parameter space in which resonance tuning occurs and the stability of the resultant periodic motion.

The purpose of this dissertation was to gain insight into spinal sensory regulation during locomotion. To this end, I developed a novel in vitro spinal cord-hindlimb preparation (SCHP) composed of the isolated in vitro neonatal rat spinal cord oriented dorsal-up with intact hindlimbs locomoting on a custom-built treadmill or instrumented force platforms. The SCHP combines the neural and pharmacological accessibility of classic in vitro spinal cord preparations with intact sensory feedback from physiological hindlimb movements. thereby expanding our ability to study spinal sensory function. I then validated the efficacy of the SCHP for studying behaviorally-relevant, sensory-modulated locomotion by showing the impact of sensory feedback on in vitro locomotion. When locomotion was activated by serotonin and N-methyl D-aspartate, the SCHP produced kinematics and muscle activation patterns similar to the intact rat. The mechanosensory environment could significantly alter SCHP kinematics and muscle activitation patterns, showing that sensory feedback regulates in vitro spinal function. I further demonstrated that sensory feedback could reinforce or initiate SCHP locomotion. Using the SCHP custom-designed force platform system, I then investigated how presynaptic inhibition dynamically regulates sensory feedback during locomotion and how hindlimb mechanics influence this regulation. I hypothesized that contralateral limb mechanics would modulate presynaptic inhibition on the ipsilateral limb. My results indicate that contralateral limb stance-phase loading regulates ipsilateral swing-phase sensory inflow. As contralateral stance-phase force increases, contralateral afferents act via a GABAergic pathway to increase ipsilateral presynaptic inhibition, thereby inhibiting sensory feedback entering the spinal cord. Such force-sensitive contralateral presynaptic inhibition may help preserve swing, coordinate the limbs during locomotion, and adjust the sensorimotor strategy for task-specific demands. This work has important implications for sensorimotor rehabilitation. After spinal cord injury, sensory feedback is one of the few remaining inputs available for accessing spinal locomotor circuitry. Therefore, understanding how sensory feedback regulates and reinforces spinally-generated locomotion is vital for designing effective rehabilitation strategies. Further, sensory regulation is degraded by many neural insults, including spinal cord injury, Parkinson's disease, and stroke, resulting in spasticity and impaired locomotor function. This work suggests that contralateral limb loading may be an important variable for restoring appropriate sensory regulation during locomotion.

<p>Locomotion is one of the most important behaviours and requires interaction between sensors at various levels of the nervous system and the limb muscles of an animal. The basic neural rhythm for locomotion in mammals has been shown to arise from local neural networks residing in the spinal cord and these networks are known as central pattern generators (CPGs). However, during the locomotion, these centres are constantly interacting with the sensory feedback signals coming from muscles, joints and peripheral skin receptors in order to adapt the stepping to varying environmental conditions. Conceptual models of mammalian locomotion have been constructed using</p><p>mathematical models of locomotor subsystems based on the abundance of neurophysiological evidence obtained primarily in the cat. Several aspects of locomotor control using the cat as an animal model have been investigated employing computer simulations and here we use the same approach to address number of questions or/and hypotheses related to rhythmic locomotion in quadrupeds. Some of the involve questions are, role of mechanical linkage during deafferented walking, finding inherent stabilities/instabilities of muscle-joint interactions during normal walking, estimating phase dependent controlability of muscle action over joints.</p><p>This thesis presents the basics of a biologically realistic model of mammalian locomotion and summarises methodological approaches in modelling quadruped locomotor subsystems such as CPGs, limb muscles and sensory pathways. In the first appended article, we extensively discuss the construction details of the three-dimensional computer simulator for the study of the hind leg neuro-musculo-skeletal-control system and its interactions during normal walking of the cat. The simulator with the walking model is programmed in Python scripting language with other supported open source libraries such as Open Dynamics Engine (ODE) for simulating body dynamics and OpenGL for three dimensional graphical representation. We have examined the</p><p>functionality of the simulator and the walking model by simulating deafferented walking. It was possible to obtain a realistic stepping in the hind legs even without sensory feedback to the two controllers (CPGs) for each leg. We conclude that the mechanical linkages between the legs also play a major role in producing alternating gait.</p><p>The use of simulations of walking in the cat for gaining insights into more complex interactions between the environment and the neuro-muscular-skeletal system is important especially for questions where a direct neurophysiological experiment can not be performed on a real walking animal. For instance, it is experimentally hard to isolate individual mechanisms without disrupting the natural walking pattern. In the second article, we introduce a different approach where we use the walking model to identify what control is necessary to maintain stability in the musculo-skeletal system. We show that the actions of most of the hindlimb muscles over the joints have an inherent stability during stepping, even without the involvement of proprioceptive feedback mechanisms. In addition, we observe that muscles generating movements in the ankle joint of the hind leg must be controlled by neural mechanisms, which may involve supraspinal structures, over the whole step cycle.</p>

Introdução: O objetivo desse estudo foi investigar o efeito da instrução para ativação consciente da musculatura abdominal sobre a atividade dos músculos escapulotorácicos durante exercícios de ombro. Métodos: Foram avaliados sessenta e cinco indivíduos assintomáticos do sexo feminino e masculino (média de idade de 23,5 ± 3 anos). Cinco exercícios enfocados no músculo serrátil anterior foram avaliados antes e depois do comando verbal e do estímulo táctil para ativação da musculatura abdominal. Foi utilizado o teste ANOVA para medidas repetitivas com teste Bonferroni post-hoc para comparar os valores eletromiográficos normalizados. Tamanhos de efeito com magnitudes moderadas e grandes foram considerados indicadores de significância em termos práticos. Resultados: Ativação consciente dos músculos abdominais resultou em um incremento significativo (p<,05) na atividade eletromiográfica dos músculos serrátil anterior e trapézio em suas fibras descendente, transversa e ascendente durante os exercícios dinâmicos (Wall Slide, Wall Press e Knee Push). A instrução aumentou a atividade eletromiográfica somente do músculo serrátil anterior durante os exercícios isométricos (Inferior Glide e Isometric Low Row). Conclusão: Ativação consciente dos músculos abdominais incentivada por comando verbal e estímulo tátil foi efetiva para incrementar a ativação dos músculos escapulotorácicos durante exercícios de ombro, principalmente para o músculo serrátil anterior com um tamanho de efeito de moderado a grande. / Introduction: The purpose of this study was to investigate the effect of the instruction for conscious contraction of the abdominal muscles on the scapulothoracic muscles activation during shoulder exercises. Methods: Sixty healthy male and female subjects (mean age 23.5 ± 3 years) volunteered for this study. Five exercises focusing on the serratus anterior muscle were assessed before and after standardized verbal, and tactile feedback applied to encourage abdominal muscle contraction. Repeated measures ANOVA and Bonferroni post-hoc test were used to compare normalized EMG amplitudes. Moderate and large magnitudes of effect size were considered indicators of the practical significance of our findings. Results: Conscious contraction of the abdominal muscles resulted in significant increase (p<.05) in serratus anterior, upper, middle and lower trapezius EMG amplitude, during dynamic exercises (Wall Slide, Wall Press, and Knee Push). Instruction increased EMG amplitude only for serratus anterior muscle during isometric exercises (Inferior Glide and Isometric Low Row). Conclusion: Conscious activation of the abdominal muscles, encouraged by verbal and tactile feedback was effective to increase the activation of periscapular muscles during shoulder exercises, in particular, the serratus anterior with large and moderate magnitudes of effect size.