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Undesirable landing area (e. g. , a hole, a fragment of glass, a water puddle, etc) creates the necessity for an alternate foot placement planning and execution. Previous study has proposed that three determinants are used by the central nervous system (CNS) for planning an alternate foot placement: minimum foot displacement, stability and maintenance of forward progression. However, validation of these determinants is lacking. Therefore, the general purpose of the series of studies presented here is to validate and test the generality of the decision algorithm of alternate foot placement selection developed previously. The first study was designed to validate the use of a virtual planar obstacle paradigm and the economy assumption behind minimum foot displacement determinant. Participants performed two blocks of trials. In one block, they were instructed to avoid stepping in a virtual planar obstacle projected in the screen of a LCD monitor embedded in the ground. In another block, they were instructed to avoid stepping in a real hole present in walkway. Behavioral response was unaffected by the presence of a real hole. In addition, it was suggested that minimum foot displacement results in minimum changes in EMG activity which validates the economy determinant. The second study was proposed to validate the stability determinant. Participants performed an avoidance task under two conditions: free and forced. In the free condition participants freely chose where to land in order to avoid stepping in a virtual obstacle. In the forced condition, a green arrow was projected over the obstacle indicating the direction of the alternate foot placement. The data from the free condition was used to determine the preferred alternate foot placement whereas the data from the forced condition was used to assess whole body stability. It was found that long and lateral foot placements are preferred because they result in a more stable behavior. The third study was designed to validate the alternate foot placement model in a more complex terrain. Participants were required to avoid stepping in two virtual planar obstacles placed in sequence. It was found that participants used the strategy of planning the avoidance movement globally and additional determinants were used. One of the additional determinants was implementation feasibility. In the third study, gaze behavior was also monitored and two behaviors emerged from this data. One sub-group of participants fixated on the area stepped during adaptive step, whereas another sub-group anchor their gaze in a spot ahead of the area-to-be avoided and used peripheral vision for controlling foot landing. In summary, this thesis validates the three determinants for the alternate foot placement planning model and extends the previous model to more complex terrains.

This dissertation demonstrates a new method for inferring a representation of the motor command, generated by the central nervous system for interactive point-to-point movements. This new tool, the input inference neural network or IINN, allows estimation of the complexity of the motor command. The IINN was applied to experimental data gathered from 7 volunteer subjects who performed point-to-point tasks while interacting with a specially constructed haptic robot. The motor plan inference demonstrates that, for the point-to-point movement tasks executed during experiments, the motor command can be projected onto a low-dimensional manifold. This dimension is estimated to be 4 or 5 and far less than the degrees of freedom available in the arm. It is hypothesized that subjects simplify the problem of adapting to changing environments by projecting the motor control problem onto a motor manifold of low dimension. Reducing the dimension of the movement optimization problem through the development of a motor manifold can explain rapid adaptation to new motor tasks.

This dissertation demonstrates a new method for inferring a representation of the motor command, generated by the central nervous system for interactive point-to-point movements. This new tool, the input inference neural network or IINN, allows estimation of the complexity of the motor command. The IINN was applied to experimental data gathered from 7 volunteer subjects who performed point-to-point tasks while interacting with a specially constructed haptic robot. The motor plan inference demonstrates that, for the point-to-point movement tasks executed during experiments, the motor command can be projected onto a low-dimensional manifold. This dimension is estimated to be 4 or 5 and far less than the degrees of freedom available in the arm. It is hypothesized that subjects simplify the problem of adapting to changing environments by projecting the motor control problem onto a motor manifold of low dimension. Reducing the dimension of the movement optimization problem through the development of a motor manifold can explain rapid adaptation to new motor tasks.

Undesirable landing area (e. g. , a hole, a fragment of glass, a water puddle, etc) creates the necessity for an alternate foot placement planning and execution. Previous study has proposed that three determinants are used by the central nervous system (CNS) for planning an alternate foot placement: minimum foot displacement, stability and maintenance of forward progression. However, validation of these determinants is lacking. Therefore, the general purpose of the series of studies presented here is to validate and test the generality of the decision algorithm of alternate foot placement selection developed previously. The first study was designed to validate the use of a virtual planar obstacle paradigm and the economy assumption behind minimum foot displacement determinant. Participants performed two blocks of trials. In one block, they were instructed to avoid stepping in a virtual planar obstacle projected in the screen of a LCD monitor embedded in the ground. In another block, they were instructed to avoid stepping in a real hole present in walkway. Behavioral response was unaffected by the presence of a real hole. In addition, it was suggested that minimum foot displacement results in minimum changes in EMG activity which validates the economy determinant. The second study was proposed to validate the stability determinant. Participants performed an avoidance task under two conditions: free and forced. In the free condition participants freely chose where to land in order to avoid stepping in a virtual obstacle. In the forced condition, a green arrow was projected over the obstacle indicating the direction of the alternate foot placement. The data from the free condition was used to determine the preferred alternate foot placement whereas the data from the forced condition was used to assess whole body stability. It was found that long and lateral foot placements are preferred because they result in a more stable behavior. The third study was designed to validate the alternate foot placement model in a more complex terrain. Participants were required to avoid stepping in two virtual planar obstacles placed in sequence. It was found that participants used the strategy of planning the avoidance movement globally and additional determinants were used. One of the additional determinants was implementation feasibility. In the third study, gaze behavior was also monitored and two behaviors emerged from this data. One sub-group of participants fixated on the area stepped during adaptive step, whereas another sub-group anchor their gaze in a spot ahead of the area-to-be avoided and used peripheral vision for controlling foot landing. In summary, this thesis validates the three determinants for the alternate foot placement planning model and extends the previous model to more complex terrains.

Orientador: Fernando Antonio Campos Gomide / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-10T00:48:57Z (GMT). No. of bitstreams: 1 Tazoniero_Alexandre_M.pdf: 2202986 bytes, checksum: eac2bab1d27c5baaf56ef296663e1cef (MD5) Previous issue date: 2007 / Resumo: O transporte ferroviário tem grande participação no transporte de cargas e passageiros em todo o mundo. No Brasil a malha ferroviária sofreu um processo de abandono e deterioração no período de 1960 a 1990. A partir de 1990 a privatização da rede ferroviária nacional iniciou uma retomada de investimentos e nos últimos anos à demanda por transporte ferroviário vem crescendo significativamente. É necessário, então, que os recursos da ferrovia sejam utilizados de maneira eficiente para atender a crescente demanda, o que exige planejamento estratégico, táctico e operacional. No nível operacional uma das principais etapas e também umas das mais carentes de ferramentas computacionais é o Planejamento de Circulação de trens. O processo operacional de uma ferrovia é dinâmico, sujeito a inúmeras interferências imprevisíveis e uma ferramenta computacional para o apoio ao planejamento de circulação de trens deve fornecer soluções com tempo de processamento compatível com essa realidade. Este trabalho propõe algoritmos para o planejamento de circulação de trens em tempo real, utilizando metodologias de inteligência computacional e conjuntos nebulosos. Um algoritmo objetiva decidir localmente a preferência entre trens concorrendo pelo uso de um segmento de linha singela de modo a seguir uma referência de percurso fornecida por algum algoritmo de otimização ou por um especialista. Outro algoritmo decide, além da preferência entre trens, a velocidade de percurso dos trens para mantê-los o mais próximo possível de suas referências. O terceiro algoritmo usa elementos de busca em árvore para obter uma solução para o planejamento de circulação de trens. É feito um estudo comparativo dos algoritmos aqui propostos e de algoritmos existentes na literatura. O estudo comparativo é feito a pm1ir de instâncias pequenas de problema de planejamento de circulação e uma instância que considera dados reais de uma ferrovia brasileira. Os resultados mostram que os algoritmos propostos obtêm soluções próximas às ótimas para as instâncias pequenas e soluções satisfatórias para o caso real / Abstract: Railways plays a major role in freight and passenger transportation in the whole world. The Brazilian railway system has suffered a process of abandon and deterioration from 1960 to 1990. Since 1990 the privatization of the national railways brought new investments and in the last years the demand for railway transportation has increased significantly. Railway resources must be efficiently managed to match the increasingly transportation demand. This requires efficient strategic, tactical and operational planning. One of the main tasks at the operational planning level concerns train circulation and associated tools. Railway operation is a very dynamic process because trains are subject to many unexpected interferences. Computational tools to help trains circulation planning must provide solutions in a time range consistent with real-time needs. This work suggests algorithms for real-time train movement planning, using computational intelligence and fuzzy set theory methodology. One of the algorithms decides the preference between trains competing for a single line track at the same moment. The aim is to drive train circulation as dose as possible to reference trajectories supplied by human experts, global optimization algorithms or both. Other algorithm decides preference between trains and chose the velocity with which trains must travel to remain as dose as possible to its references. The third algorithm uses depth search algorithm to obtain a solution for train circulation problems. A comparative study considering the algorithms proposed herein and algorithms suggested in the literature. The comparative study is done using small railway system instances. Data of a major Brazilian railway is adopted to illustrate how the algorithms behave to solve larger instances. Results show that the algorithms here proposed obtain near optimal solutions for small instances and satisfactory solutions for the real case / Mestrado / Automação / Mestre em Engenharia Elétrica

The purpose of this study was to explore differences in movement initiation and execution, and their associations with amount of physical activity (PA) and cognitive abilities, in 6 to 8 year old children born PT compared to peers born at term. The sample consisted of in total 78 children divided in subgroups, 16 born very preterm (VPT), 24 born moderate preterm (MPT) and 38 age matched controls born at term (FT) with no diagnosed cognitive or motor impairments. Three-dimensional (3D) kinematic recordings of wrist movements during two bimanual tapping tasks (horizontal and vertical) were finalized and kinematic outcome measures were investigated in relation to PA and performance on WISC-IV. Children born VPT showed significantly longer Latency times and longer Duration of movement execution compared to children born MPT and FT. No significant within group correlations between PA and movement performance were found. Duration of movement execution and Total duration of movement execution were negatively associated with Full-scale intelligence quotient (FSIQ) and processing speed index (SI) in the PT group. Early school aged children born VPT need longer planning time to initiate and execute goal directed bimanual movements, compared to peers born MPT and FT. Kinematic performance did not evidently associate with amount of PA, although kinematics, by means of longer Latency time and Duration of movement execution, negatively associated with SI. / Syftet med denna studie var att undersöka skillnader i initiering och utförande av en rörelse samt deras associationer med fysisk aktivitet och kognitiv förmåga hos förtidigt födda barn i åldrarna 6 till 8 år samt åldersmatchade fullgångna jämnåriga barn. Urvalet bestod av total 78 barn uppdelade i subgrupper, 16 väldigt förtidigt födda, 24 moderat förtidigt födda och 38 åldersmatchade fullgångna kontroller utan några kända kognitiva eller motoriska nedsättningar. Tredimensionella (3D) kinematiska registreringar av handledsrörelser under två bimanuella knapptrycksuppgifter (horisontell och vertikal) genomfördes. Utfallet av rörelsemätningarna studerades i association till fysisk aktivitet och resultat på WISC-IV. Väldigt förtidigt födda barn visade längre latenstid och längre duration av rörelse jämfört med moderat förtidigt födda och fullgångna barn. Inga signifikanta inom grupps korrelationer mellan fysisk aktivitet och rörelseutförande hittades. Utförandets duration samt hela utförandets duration associerade negativt med IQ kvot och processhastighet (SI) hos för tidigt födda barn. Väldigt förtidigt födda barn i tidig skolålder behöver mer tid till rörelseplanering, initiering och utförande av viljestyrda målinriktade rörelser jämfört med jämnåriga barn födda senare i graviditeten. Kinematiskt utfall associerade inte signifikant med fysisk aktivitet, däremot associerade kinematiskt utfall, i form av längre latenstid och duration av utförande, negativt med kognitiv processhastighet.

La vision fournit des informations essentielles sur la surface de marche, ainsi que sur la taille, la forme et la position d’obstacles potentiels dans notre environnement. Dans le cas d’un prédateur, la vision fournit également des informations sur la vitesse d’une proie potentielle. Les mécanismes neuronaux impliqués dans l’exécution des modifications de la marche sous guidage visuel sont relativement bien connus, mais ceux impliqués dans la planification de ces modifications de la marche sont peu étudiés. Le cortex pariétal postérieur (CPP) semble être un candidat approprié si l’on considère les propriétés du CPP lors des mouvements d’atteinte vers une cible. Le but des présents travaux est de déterminer la contribution du CPP au contrôle de la locomotion sous guidage visuel. La première étude présentée dans cette thèse a pour hypothèse que le CPP du chat est impliqué dans la planification du placement précis du pied lors des modifications volontaires de la marche. Nous avons entraîné les animaux à enjamber des obstacles en mouvement attachés à la ceinture d’un tapis roulant. Afin d’augmenter la nécessité d’intégrer les informations visuelles et proprioceptives, nous avons dissocié la vitesse des obstacles de celle du tapis roulant. Nous avons observé que plus la vision devient critique pour la tâche, plus les déficits sont importants. Notre analyse démontre que ceux-ci résultent d’un placement inapproprié du pied dans le cycle de marche précédant l’enjambement de l’obstacle. Ceci suggère que le CPP est impliqué dans la planification du placement précis du pied pendant la locomotion sous guidage visuel. La vision directe est disponible lors de la modification de l’activité des membres antérieurs, mais n’est plus disponible lorsque l’obstacle passe sous le corps. Par conséquent, la modification de l’activité des membres postérieurs doit être basée sur l’information gardée en mémoire et coordonnée avec celle des membres antérieurs. Notre deuxième étude a pour but de caractériser les mécanismes neuronaux responsables de cette coordination. Nous avons proposé que le CPP soit impliqué dans la coordination des membres antérieurs et postérieurs lors de l’enjambement d’obstacles. Pour tester cette hypothèse, nous avons enregistré l’activité de neurones de l’aire 5 pendant la même tâche. Nous avons découvert deux populations: une qui décharge lors du passage de l’obstacle entre les membres antérieurs et postérieurs et une autre qui décharge lors du passage de l’obstacle par les membres postérieurs. Dans la tâche de dissociation visuelle, la décharge est modifiée en fonction du temps de passage de l’obstacle sous le corps et reflète la modification du couplage entre les membres lors du changement dans la stratégie d’enjambement. De plus, ces mêmes neurones maintiennent une décharge soutenue lorsqu’un obstacle fixe se trouve entre les membres antérieurs et postérieurs ou les deux membres postérieurs (limite testée : 1-2min). Ces neurones pourraient être responsables de l’emmagasinage à plus long terme des caractéristiques d’un obstacle pour le guidage des mouvements des membres postérieurs. Nos résultats suggèrent que le CPP est impliqué dans l’intégration des informations visuelles et proprioceptives pour la planification du placement précis du pied devant un obstacle. Le patron de décharge de nos populations neuronales suggère qu’il encode également l’information temporelle et spatiale concernant la vitesse et la position de l’obstacle afin de coordonner l’activité des quatre membres pendant la tâche. Finalement, nous proposons qu’une des fonctions du CPP soit d’estimer la position des membres par rapport à l’obstacle en mouvement. / During locomotion, vision provides crucial information about the type of terrain one walks on, as well as the size, shape and location of possible obstacles in the path. In the case of a predator, vision also provides information about the speed of a potential prey. The neuronal mechanisms involved in the execution of visually guided gait modifications are now well studied, but those related to their planning remain poorly understood. One likely candidate involved in movement planning is the posterior parietal cortex (PPC). Based on a consideration of the properties of the PPC in visually-guided reaching, the present study was designed to determine the contribution of the PPC to the control of visually-guided locomotion. In the first study presented in this thesis, we hypothesize that the cat PPC is involved in the planning of precise foot placement during voluntary gait modifications. We trained animals to step over moving obstacles attached on a treadmill belt before and after a lesion to area 5. To increase the need for visual and proprioceptive integration, we dissociated the speed of the obstacles from that of the treadmill. We noticed that deficits were largest when the importance of vision was the greatest. Our analysis showed that the deficits were due to inappropriate paw placement prior to the step over the obstacle and thus suggests that the PPC is involved in the planning of precise paw placement during visually-guided locomotion. Direct visual information is available to guide forelimb gait modifications, but is lost when the obstacle passes under the body. Therefore, hindlimb gait modifications must rely on remembered information and must be coordinated with those of the forelimbs. Our second study is designed to determine the neuronal mechanisms responsible for this coordination. We propose that the PPC is responsible for coordinating the activity of the forelimbs and the hindlimbs during obstacle negotiation. To test this hypothesis, we recorded the activity of area 5 neurones in the same task and found two cell populations: one that discharged in relation to the passage of the obstacle between the fore and hindlimbs, and the other between the two hindlimbs. In the visual dissociation task, the discharge was modified to account for the increased time taken by the obstacle to pass under the body and the change in interlimb coupling when cats modified their stepping strategy during the step over the obstacle. We also found that these same cells maintained their discharge when the cat straddled an obstacle either between the fore and hindlimbs or between the two hindlimbs. The discharge was sustained up to the limit tested (~ 1-2min). These neurones could be responsible for the retention of obstacles characteristics to guide future hindlimb movements. Our results provide support for the hypothesis that the PPC is involved in the integration of visual and proprioceptive information for the planning of precise paw placement in front of obstacles. The discharge of our neuronal populations suggests it also encodes temporal and spatial information regarding obstacle’s location and speed to coordinate all four limbs during the task. Finally, we propose that one function of the PPC is to estimate the position of the limbs with respect to the advancing obstacle.

La vision fournit des informations essentielles sur la surface de marche, ainsi que sur la taille, la forme et la position d’obstacles potentiels dans notre environnement. Dans le cas d’un prédateur, la vision fournit également des informations sur la vitesse d’une proie potentielle. Les mécanismes neuronaux impliqués dans l’exécution des modifications de la marche sous guidage visuel sont relativement bien connus, mais ceux impliqués dans la planification de ces modifications de la marche sont peu étudiés. Le cortex pariétal postérieur (CPP) semble être un candidat approprié si l’on considère les propriétés du CPP lors des mouvements d’atteinte vers une cible. Le but des présents travaux est de déterminer la contribution du CPP au contrôle de la locomotion sous guidage visuel. La première étude présentée dans cette thèse a pour hypothèse que le CPP du chat est impliqué dans la planification du placement précis du pied lors des modifications volontaires de la marche. Nous avons entraîné les animaux à enjamber des obstacles en mouvement attachés à la ceinture d’un tapis roulant. Afin d’augmenter la nécessité d’intégrer les informations visuelles et proprioceptives, nous avons dissocié la vitesse des obstacles de celle du tapis roulant. Nous avons observé que plus la vision devient critique pour la tâche, plus les déficits sont importants. Notre analyse démontre que ceux-ci résultent d’un placement inapproprié du pied dans le cycle de marche précédant l’enjambement de l’obstacle. Ceci suggère que le CPP est impliqué dans la planification du placement précis du pied pendant la locomotion sous guidage visuel. La vision directe est disponible lors de la modification de l’activité des membres antérieurs, mais n’est plus disponible lorsque l’obstacle passe sous le corps. Par conséquent, la modification de l’activité des membres postérieurs doit être basée sur l’information gardée en mémoire et coordonnée avec celle des membres antérieurs. Notre deuxième étude a pour but de caractériser les mécanismes neuronaux responsables de cette coordination. Nous avons proposé que le CPP soit impliqué dans la coordination des membres antérieurs et postérieurs lors de l’enjambement d’obstacles. Pour tester cette hypothèse, nous avons enregistré l’activité de neurones de l’aire 5 pendant la même tâche. Nous avons découvert deux populations: une qui décharge lors du passage de l’obstacle entre les membres antérieurs et postérieurs et une autre qui décharge lors du passage de l’obstacle par les membres postérieurs. Dans la tâche de dissociation visuelle, la décharge est modifiée en fonction du temps de passage de l’obstacle sous le corps et reflète la modification du couplage entre les membres lors du changement dans la stratégie d’enjambement. De plus, ces mêmes neurones maintiennent une décharge soutenue lorsqu’un obstacle fixe se trouve entre les membres antérieurs et postérieurs ou les deux membres postérieurs (limite testée : 1-2min). Ces neurones pourraient être responsables de l’emmagasinage à plus long terme des caractéristiques d’un obstacle pour le guidage des mouvements des membres postérieurs. Nos résultats suggèrent que le CPP est impliqué dans l’intégration des informations visuelles et proprioceptives pour la planification du placement précis du pied devant un obstacle. Le patron de décharge de nos populations neuronales suggère qu’il encode également l’information temporelle et spatiale concernant la vitesse et la position de l’obstacle afin de coordonner l’activité des quatre membres pendant la tâche. Finalement, nous proposons qu’une des fonctions du CPP soit d’estimer la position des membres par rapport à l’obstacle en mouvement. / During locomotion, vision provides crucial information about the type of terrain one walks on, as well as the size, shape and location of possible obstacles in the path. In the case of a predator, vision also provides information about the speed of a potential prey. The neuronal mechanisms involved in the execution of visually guided gait modifications are now well studied, but those related to their planning remain poorly understood. One likely candidate involved in movement planning is the posterior parietal cortex (PPC). Based on a consideration of the properties of the PPC in visually-guided reaching, the present study was designed to determine the contribution of the PPC to the control of visually-guided locomotion. In the first study presented in this thesis, we hypothesize that the cat PPC is involved in the planning of precise foot placement during voluntary gait modifications. We trained animals to step over moving obstacles attached on a treadmill belt before and after a lesion to area 5. To increase the need for visual and proprioceptive integration, we dissociated the speed of the obstacles from that of the treadmill. We noticed that deficits were largest when the importance of vision was the greatest. Our analysis showed that the deficits were due to inappropriate paw placement prior to the step over the obstacle and thus suggests that the PPC is involved in the planning of precise paw placement during visually-guided locomotion. Direct visual information is available to guide forelimb gait modifications, but is lost when the obstacle passes under the body. Therefore, hindlimb gait modifications must rely on remembered information and must be coordinated with those of the forelimbs. Our second study is designed to determine the neuronal mechanisms responsible for this coordination. We propose that the PPC is responsible for coordinating the activity of the forelimbs and the hindlimbs during obstacle negotiation. To test this hypothesis, we recorded the activity of area 5 neurones in the same task and found two cell populations: one that discharged in relation to the passage of the obstacle between the fore and hindlimbs, and the other between the two hindlimbs. In the visual dissociation task, the discharge was modified to account for the increased time taken by the obstacle to pass under the body and the change in interlimb coupling when cats modified their stepping strategy during the step over the obstacle. We also found that these same cells maintained their discharge when the cat straddled an obstacle either between the fore and hindlimbs or between the two hindlimbs. The discharge was sustained up to the limit tested (~ 1-2min). These neurones could be responsible for the retention of obstacles characteristics to guide future hindlimb movements. Our results provide support for the hypothesis that the PPC is involved in the integration of visual and proprioceptive information for the planning of precise paw placement in front of obstacles. The discharge of our neuronal populations suggests it also encodes temporal and spatial information regarding obstacle’s location and speed to coordinate all four limbs during the task. Finally, we propose that one function of the PPC is to estimate the position of the limbs with respect to the advancing obstacle.