Seventy percent of stroke survivors experience loss of upper limb function after stroke and rehabilitative therapy is the only option to reduce impairments. However, uncertainty remains as to the optimal dose of therapy that should be prescribed. It has been suggested to report multiple parameters of dose, to increase standardization within the field, and to gain a better understanding of the dose-response relationship. This study investigated the automatic quantification of multiple dose parameters in a rat model of ischemic stroke, with rehabilitation paradigms whereby rats repeatedly grasp for food pellets to train their forelimb function. Starting 7 days post-stroke, groups of rats received 4, 8, or 12 rehabilitative training sessions for 10 days, practicing either high-quality (precision practice) or less skilled (mass practice) reaching movements. Pellet consumption was measured after each session and various metrics were analyzed using deep learning-based software (DeepLabCut, DLC) to represent parameters of dose intensity (number of reaches, paw path length) and session density (time on task). Functional outcome was assessed with the Montoya staircase task. Computer algorithms were validated against human analysis, demonstrating reach detection accuracy and reliability >80%. Interestingly, the number of training sessions did not alter the accumulated movement practice across rehabilitation, in either task. However, the number of sessions inversely affected training intensity, resulting in more forelimb use per session in rats with 4 sessions compared to 12 sessions. We found strong positive correlations between the number of reaches, time on task, paw path length, and pellets consumed in the precision practice, but only between reaches and pellets consumed in mass practice. This work demonstrates the quantification of multiple dose parameters using deep learning software and shows subtle differences between the two commonly used forelimb training tasks. Moreover, our data suggest that rehabilitative training at a frequency that is too high may negatively impact performance per session.

No description available.

Handedness is a widely studied behavioral asymmetry that is commonly measured as a preference for using one hand over the other. Right hand preference in humans occurs at a ratio of 9:1, whereas left hand preference in rhesus monkeys has been estimated at 2:1. Despite differences in the direction and degree of hand preference, this dissertation investigated whether primates share common underlying factors for the development of handedness. Previous work in human infants has identified a predictive relationship between rightward supine head orientation and later right hand preference. Experiment 1 examined the relationship between neonatal head orientation and later hand use in rhesus monkey infants (N=16). A leftward supine head orientation bias was found that corresponded to greater left hand activity for hand-to-face movements while supine; however, neonatal head positioning did not predict later hand use preference for reaching or manipulation on a coordinated bimanual task. A supine posture is common for human infants, but not for rhesus monkey infants, indicating that differences in early posture experience may differentially shape the development of hand use preference. Movement quality is an additional factor that may affect how the hands are used in addition to neonatal experience. 2-D and 3-D kinematic analyses were used to examine the quality of reaching movements in rhesus monkey infants (N=16), human infants (N=73) and human adults (N=12). In rhesus monkey infants, left hand reaches were characterized as ballistic as compared to right hand reaches independent of hand use preference (Experiment 2). Left hand ballistic reaching in rhesus monkeys may be a carryover from earlier primates that relied on very fast reaches to capture insect prey. Unlike monkey infants, reach quality was a function of hand preference in human infants (Experiment 3). By contrast, a right hand advantage for reaching was observed in human adults regardless of left or right hand preference (Experiment 4). Differential hand experience due to hand preference in early infancy may in part be responsible for the hand preference effects on movement quality observed in human infants but not monkey infants. Motor control may become increasingly lateralized to the left hemisphere over human development leading to the right hand advantage for reaching observed in human adults, as well as over primate evolution leading to right hand use preferences in higher primates like chimpanzees. An underlying mechanism such as a right shift factor in humans and a left shift factor in rhesus monkeys may be a common basis for primate handedness. Environmental and experiential factors then differentially shape this mechanism, including species-typical development. Further work examining the ontogeny of hand preference and hemispheric specialization in various primate infants will lead to a greater understanding of how different factors interact in the development of hand use across primate species.

No description available.

<p>A fundamental decision when interacting with objects in our environment involves hand selection. Two major factors that influence this choice include handedness (the proficiency of one hand over the other) and the spatial relationships perceived between the object and both effectors (Gabbard & Rabb, 2000). Previous studies have altered the location of an object in space and the complexity of a task as it relates to hand choice decisions (Bryden et al., 2003; Gabbard et al., 2003; Mamalo et al., 2006). This thesis investigates the idea of reaching toward a series of predictable target locations and its effect on the frequency of hand use when compared to unpredictable reaches. Predictable reaches allow participants to assign hand use prior to movement initiation. Participants reached to a series of 3-target sequences in one of two groups: unpredictable reaches, selecting a hand to reach each target as it appeared; and predictable reaches, where the target sequence was presented prior to initiating a reach. Unpredictable reaches at different hand positions in space demonstrate that object proximity often mediates hand choice by promoting use of the effector that affords the shortest reaching amplitude. Further, predictive reaches demonstrate a preference to complete larger reaching amplitudes earlier in the sequence in order to place both hands in a position where object proximity mediates hand choice later in the sequence. Overall, predictable reaches seem to resemble the end-state comfort effect (Rosenbaum, 1992), where participants change their approach to executing reaches when they know the sequence of targets that follows.</p> / Master of Science in Kinesiology

Smooth tracking and efficient reaching for moving objects require the ability to predict the velocity and trajectory of the object. This skill is important to be able to perceive human action and object motion in the world. This thesis explores early visual motor development in full term and preterm infants. Study I showed that horizontal eye tracking develops ahead of vertical (full term infants at 5, 7 and 9 months of age). The vertical component is also more affected when a second dimension is added during circular pursuit. It is concluded that different mechanisms appear to underlie vertical and horizontal eye movements Study II-IV compared the development of the ability to visually track and reach for moving objects in very preterm infants born &lt;32 gestational weeks to healthy infants born at term. The development of horizontal smooth pursuit at 2 and 4 months of corrected age was delayed for the preterm group (Study II). Some infants were catching up whereas others were not improving at all. A question raised by the results was whether the delay was caused by specific injuries as a result of the prematurity. However, the delays persisted when all infants with known neonatal complications and infants born small for gestational age were excluded (Study III), indicating that they were caused by prematurity per se. At 8 months corrected age preterm and full term infants were equally good at aiming reaches and successfully catching a moving object. Nevertheless, the preterm group used a bimanual strategy more often and had a more jerky and circuitous path than the full term group (Study IV). In summary, preterm infants showed a delayed visual motor development compared to infants born at term. The results of these studies suggest that there is additional diffuse damage to the visual motor system that is not related to neonatal complications as diagnosed today. Measuring smooth pursuit could potentially be a new method for early non-invasive diagnosis of impaired visual function.

The works reported in this thesis focus upon synthesising neural controllers for anthropomorphic robots that are able to manipulate objects through an automatic design process based on artificial evolution. The use of Evolutionary Robotics makes it possible to reduce the characteristics and parameters specified by the designer to a minimum, and the robot’s skills evolve as it interacts with the environment. The primary objective of these experiments is to investigate whether neural controllers that are regulating the state of the motors on the basis of the current and previously experienced sensors (i.e. without relying on an inverse model) can enable the robots to solve such complex tasks. Another objective of these experiments is to investigate whether the Evolutionary Robotics approach can be successfully applied to scenarios that are significantly more complex than those to which it is typically applied (in terms of the complexity of the robot’s morphology, the size of the neural controller, and the complexity of the task). The obtained results indicate that skills such as reaching, grasping, and discriminating among objects can be accomplished without the need to learn precise inverse internal models of the arm/hand structure. This would also support the hypothesis that the human central nervous system (cns) does necessarily have internal models of the limbs (not excluding the fact that it might possess such models for other purposes), but can act by shifting the equilibrium points/cycles of the underlying musculoskeletal system. Consequently, the resulting controllers of such fundamental skills would be less complex. Thus, the learning of more complex behaviours will be easier to design because the underlying controller of the arm/hand structure is less complex. Moreover, the obtained results also show how evolved robots exploit sensory-motor coordination in order to accomplish their tasks.

O movimento de alcançar e de pegar objetos é amplamente utilizado nas atividades diárias. Desta forma, diversos estudos têm analisado e descrito este padrão de movimento em função de diferentes aspectos que influenciam seu controle. Da mesma forma, o movimento de andar é uma habilidade fundamental nas atividades diárias e tem sido estudado e descrito amplamente na literatura. Entretanto, pouco se sabe sobre quais são as alterações que ocorrem nessas habilidades motoras quando elas são combinadas. A realização combinada de habilidades motoras (ex., andar e pegar um objeto) está muito presente no dia a dia das pessoas, mas o entendimento do controle desse tipo de tarefa combinada ainda não foi elucidado. Adicionalmente, ainda não está claro quais são as modificações que ocorrem nestes movimentos em função do processo de envelhecimento e do histórico de quedas recentes em idosos. Desta forma, três estudos foram conduzidos para investigar o desempenho motor de adultos jovens e idosos com e sem histórico de quedas na marcha combinada com o movimento de preensão em função do nível de dificuldade da tarefa manual. O primeiro estudo investigou o desempenho motor dos adultos jovens na marcha combinada com o movimento de preensão. O segundo estudo comparou o desempenho motor entre idosos com e sem histórico de quedas na marcha combinada com o movimento de preensão. Ainda, o terceiro estudo comparou o padrão de coordenação entre idosos (com e sem histórico de quedas) e adultos jovens na marcha combinada com o movimento de preensão. Participaram desta tese, 45 indivíduos distribuídos em três grupos (n=15): adultos jovens, idosos sem histórico de quedas e idosos com histórico de quedas. Os indivíduos foram convidados a alcançar e pegar um objeto em duas tarefas (manutenção da postura ereta e marcha) e para cada uma, seis condições experimentais foram realizadas com diferentes níveis de dificuldade. Para analisar o movimento de preensão, movimentos do corpo todo e os parâmetros espaço-temporais da marcha, um sistema tridimensional de análise de movimento foi utilizado. Modificações na marcha e no movimento de preensão foram identificados quando combinados, especialmente para as condições mais desafiadoras da tarefa manual. A adição da tarefa de pegar o objeto provocou uma adaptação na marcha, pois os participantes adotaram uma estratégia mais conservadora para aumentar a estabilidade dinâmica durante a fase de aproximação. Assim é possível sugerir que o movimento de preensão foi sobreposto ao da marcha, embora as adaptações no comportamento motor sejam globais, pois ambos os padrões motores (marcha e preensão) foram modificados para realizar com sucesso a tarefa em função dos diferentes níveis de dificuldade da tarefa manual. Os idosos com histórico de quedas apresentaram um desempenho motor inferior aos idosos sem histórico de quedas na marcha combinada com o movimento de preensão, como por exemplo, redução na velocidade do passo, aumento na duração do passo, redução na velocidade do punho e na abertura entre os dedos. Além disso, os idosos com histórico de quedas apresentaram maior redução na velocidade do COM AP em comparação com os idosos sem histórico de quedas. Assim, o paradigma de tarefas combinadas desenvolvido no presente estudo identificou mudanças nas estratégias de controle motor em idosos caidores, sendo que estas alterações foram ainda mais evidenciadas nas condições manuais mais difíceis. Ainda, a adição da tarefa de pegar o objeto na marcha modificou o padrão de coordenação entre membros superiores e inferiores para os movimentos de flexão/extensão e abdução/adução. Assim, para os movimentos de flexão e extensão, um padrão mais em fase e menos fora de fase foi identificado na condição de preensão comparado com a marcha livre quando o ombro direito foi analisado em relação ao ombro esquerdo e quadril direito. Para os movimentos de abdução e adução, quando o movimento de ombro direito foi analisado em relação ao ombro esquerdo e quadril direito, foi observado um padrão menos em fase. Além disso, um padrão menos fora de fase foi observado para os acoplamentos entre ombro direito-ombro esquerdo e ombro direito-quadril esquerdo. Entretanto, estas mudanças no padrão de coordenação não foram afetadas pelo nível de dificuldade manual. Este resultado sugere que as mudanças no padrão de coordenação são mais globais, enquanto mudanças específicas no movimento de membro superior são necessárias para acomodar as diferentes demandas da tarefa manual. Finalmente, idosos com histórico de quedas apresentaram um padrão diferente de coordenação quando comparados com os adultos jovens, como por exemplo, um padrão mais fora de fase para o acoplamento entre ombro direito e quadril direito e um padrão menos fora de fase para o acoplamento entre ombro direito e quadril esquerdo na marcha combinada com o movimento de preensão. Desta forma, parece que os idosos com histórico de quedas desacoplam a tarefa da marcha combinada com o movimento de preensão, diferentes dos adultos jovens e idosos sem histórico de quedas. / Reaching-to-grasping an object is widely used in daily activities. Many studies have analyzed and described this movement pattern considering different aspects that influence how it is controlled. Likewise, walking is a fundamental skill in daily activities and has been studied and described widely in the literature. However, little is known about what are the changes that occur in these motor skills when they are combined. The combined performance of motor skills (e.g. walk and grasp an object) is very common in daily life activities, but the understanding of the control mechanisms of this type of task is lacking. In addition, it is not clear what are the changes that occur in these movements due to aging and changes in balance control as observed in older adults with history of falls. Thus, three studies were designed to investigate the motor performance of young adults and older adults with and without history of falls during walking combined with prehension. The first study investigated motor performance of young adults while performing the combined task of walk and prehension at different levels of difficulty of the manual task. The second study investigated the same combined task with different levels of manual task difficulty in older adults with and without history of falls. Yet, the third study investigated the interlimb coordination pattern in young and older adults with and without history of falls during the combined task of walking and prehension with different levels of manual task difficulty. Forty-five individuals, distributed in three groups (young adults; older adults without history of falls; older adults with history of falls), participated in this study. They performed the reach-to-grasp movement in two tasks (upright stance and gait) involving six experimental condition with different levels of manual difficulty. To analyze prehension, body movements and spatio-temporal gait parameters, a tridimensional movement analysis system was used. Modifications in gait and prehension were identified when they were combined, especially for the most difficult prehension conditions. The grasping task caused an adaptation in gait since participants preferred to adopt a more conservative strategy, increasing their dynamic stability during the approach phase and when grasping the dowel. Based on these results, it is possible to suggest that prehension was superimposed on gait, although the adaptations in motor behavior were global, since both motor patterns (i.e., walking and prehension) were changed to perform the task successfully with different levels of difficulty. It is possible to suggest that motor performance of fallers in the combined task of walking and grasping is more impaired than in no-fallers (for instance, decreased step velocity, increased step duration, decreased wrist velocity and peak grip aperture velocity). Moreover, older adults with history of falls presented a greater reduction in COM AP velocity when compared to older adults without history of falls. The combined task paradigm used in the present study showed some changes in motor control strategy of fallers older adults when performing walking and prehension combined. In addition, motor patterns (walking and grasping) of older adults (fallers and no-fallers) were modified in function of the level of manual task difficulty. The analysis of the relative motion allowed the quantification of the changes in the coordination pattern of the combined task involving walking and prehension for flexion/extension and abduction/adduction movements. For flexion/extension movements, a more in-phase and a less anti-phase pattern was identified in the grasping condition compared to walking through when right shoulder was analyzed relative to left shoulder and right hip. For adduction/abduction movements, when right shoulder was analyzed relative to left shoulder and right hip, it was observed less in phase pattern. In addition, we found a less anti-phase pattern for right shoulder-left shoulder and right shoulder-left hip couplings. However, the changes in motor coordination were not affected by the manual task difficulty for young adults and older adults with and without history of falls. This result suggests that changes in coordination are more general while specific changes in upper limb movement are necessary to deal with different task demands. Finally, older adults with history of falls presented a different pattern of coordination than young adults, such as, a more anti-phase pattern for right shoulder-right hip coupling and a less anti-phase pattern for right shoulder-left hip coupling during the combined task. Thus, it seems that older adults with history of falls decouple the walking and prehension tasks, differently of young adults and older adults without history of falls.

It is well established that cathodal transcranial direct current stimulation (tDCS) can decrease the excitability of the primary motor cortex (M1) in humans. Despite the cortical inhibition caused by cathodal tDCS, it remains unknown how this intervention alters unrestrained dynamic reaching movements qualitatively. Accordingly, we designed this study to examine how cathodal tDCS impacts unrestrained dynamic reaching as measured by qualitative kinematic features and electromyography (EMG). Ten young, healthy adult subjects were recruited to participate in a two day protocol involving repetitively reaching to two different targets (large and small) both before and following cathodal tDCS applied over the contralateral M1 during one session and before and following sham tDCS over the same brain region during another session. We discovered that cathodal tDCS was not able to alter the kinematic features of reaching in these subjects but did degrade the EMG performance, specifically by increasing the amount of co-contraction between muscle pairs. Because co-contraction is an indicator of relatively unskilled performance, these results seem to indicate that cathodal tDCS of M1 preferentially disrupts the learning or execution of highly coordinated muscle firing patterns during dynamic reaching. This work adds to the growing body of knowledge about how tDCS applied over M1 affects our movements. Moreover, it leads us to believe that tDCS can be utilized to assist in rehabilitation of patient populations who suffer from neurological dysfunctions but EMG assessments may need to be included in order to more effectively assess the patient performance.

<p>Children with myelomeningocele (MMC) usually have problems with daily life activities, but the background to their problems is not altogether obvious. An understanding of the possible causes of activity problems is a prerequisite for the effectiveness of physical therapy. The overall aim of the present studies was to identify impairments above the cele level, which might influence mobility in children with MMC (study I) and to analyse sitting posture (study II) and the movement characteristics of reaching movements (study III and IV). </p><p>In total, 41 children and young adults with MMC and without mental retardation were investigated. Study I comprised 32 children, 6-11 years. Mobility and the caregiver assistance required for mobility were quantified according to the Paediatric Evaluation of Disability Inventory (PEDI) and correlation between mobility and neurological impairment, hand function and cognitive function were calculated. The results showed that nine children achieved independent mobility and that there was a moderate and significant correlation between the need for physical assistance and high cele level, impaired hand function and impaired cognitive function. In those children who used a wheelchair, only poor hand strength was significantly correlated with the need for caregiver assistance.</p><p>Study II comprised 11 children, 10-13 years, and a control group of 20 healthy children. Sitting posture was investigated by using a force plate and analysed from the frequency and the amplitude of the postural sway. The reaction forces before and during rapid arm lift were also analysed. The result showed that children with MMC had significantly lower sway frequency compared to the controls. In both groups, the ground reaction forces were registered before the children lifted their arms. Study III and IV comprised 31 children and young adults, 9-19 years and 31 matched controls. Reaching movements were investigated with a digitising tablet, linked to a computer. The ability to program and execute reaching movements was analysed and also the ability to adapt reaching to new visuomotor conditions. The results showed that the MMC group had poorer precision, less straight movements and shorter deceleration phases as compared to the controls. In both groups the movements were pre-programmed. In addition, adaptation of reaching to new visuomotor conditions was poor in the MMC group as compared to the controls. </p><p>In conclusion we found that impairments above the cele level influenced mobility and the control of sitting posture in children with MMC. Reduced precision and co-ordination of reaching, and also difficulties with motor adaptation, could partly explain thier problems with hand activities. These findings need to be considered in therapy programs for children and young adults with MMC.</p>