In this thesis, specific practice conditions were examined for skill acquisition and transfer of perceptual-cognitive-motor processes underlying dynamic and complex performance. The availability of visual and cognitive processes during practice was modulated to examine contribution of each process to the skill acquisition using a novel computer-based task where participants were required to select and execute decisions to move a cursor to a target whilst avoiding random moving objects. Results demonstrated that practice with necessary information and processes improved the task performance, whereas limiting the underlying processes attenuated skill acquisition. Subsequently, the underlying processes were examined by measuring eye movements and condition-action pairs. Successful skill acquisition was underpinned by the modified visual search and decision making processes through practice. However, limiting necessary sensory information and decoupling cognitive processing during practice developed specific sensorimotor behaviour that did not lead to successful task performance. These results provided an insight of the skill acquisition by suggesting that when a task requires the acquisition of perceptual-cognitive-motor processes to be successful, integration of these processes would be necessary, whereas decoupling of these processes would limit skill acquisition. Moreover, transfer of acquired processes was examined between two tasks. Both tasks required the acquisition of similar perceptual-cognitive processes in order to select successful cursor trajectories, but the main goal differed between tasks. In addition, for both tasks a yoked condition aimed to limit cognitive processes to investigate the role of transfer-appropriate processing in skill acquisition. Results showed positive transfer indicating that practice on another task improved performance on the other task, whereas limiting cognitive processes attenuated the skill acquisition and transfer. Transfer would be maximised when the underlying processes between practice and transfer domain are similar or matched, whereas the transfer would be attenuated when the necessary processes are decoupled during practice. The overall findings extend the research in perceptual-cognitive-motor processes and have several theoretical and applied implications.

Performing goal-directed hand-movements in the presence of obstacles is a task that we usually complete successfully many times a day without much conscious consideration. Yet, little is known about the underlying processes. The aim of this thesis was to investigate the role of perceptual, motor and cognitive constraints on obstacle avoidance during reaching. To do this a tabletop-based obstacle avoidance setup and motiontracking were used. In the first experimental chapter, the previously reported tendency of participants to select movement paths that pass roughly through the mid-point between two obstacles was examined. The starting position of the hand and the availability of visual feedback were manipulated and evidence was found that movement path selection depends on both a collision-avoidance strategy and the associated biomechanical costs; even when visual feedback is unavailable. The second experimental chapter investigated an action-blindsight phenomenon, specifically the ability of cortically blind patients to avoid unseen obstacles. It was found that only two out of the six patients tested potentially showed some residual sensitivity to obstacles in their blind visual field. The final two experimental chapters went further to examine the role of perceptual information and attentional mechanisms respectively. It was found that during obstacle avoidance participants predominantly look at the movement target and rarely towards any obstacles or their moving hand. Furthermore, they tend to move their hand away from obstacles that are fixated. Finally, it was also found that a concurrent attentional task affected movement path selection in a similar way. At present it is unclear whether these perceptual and attentional effects are additive or independent of each other. Overall, these findings suggest that both conscious visual information and attentional mechanisms are crucial factors in determining movement path selection during obstacle avoidance in reaching.

Eye fixations of the face are normally directed towards either the eyes or the mouth, however the proportions of gaze to either of these regions are dependent on context. Previous studies of gaze behavior demonstrate a tendency to stare into a target’s eyes, however no studies investigate the differences between when participants believe they are engaging in a live interaction compared to knowingly watching a pre-recorded video, a distinction that may contribute to studies of memory encoding. This study examined differences in fixation behavior for when participants falsely believed they were engaging in a real-time interaction over the internet (“Real-time stimulus”) compared to when they knew they were watching a pre-recorded video (“Pre-recorded stimulus”). Results indicated that participants fixated significantly longer towards the eyes for the pre-recorded stimulus than for the real-time stimulus, suggesting that previous studies which utilize pre-recorded videos may lack ecological validity. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

The hippocampus is necessary for normal memory in rodents, birds, monkeys, and people. Damage to the hippocampus can result in the inability to learn new facts, defined by the relationship among stimuli. In rodents, spatial learning involves learning about the relationships among stimuli, and exemplifies the kind of learning the requires the hippocampus. Therefore, understanding the neural mechanisms underlying spatial learning may elucidate basic memory processes. Many hippocampal neurons fire when behaving rats, cats, or monkeys are in circumscribed regions (place fields) of an environment. The neurons, called place cells, fire in relation to distal stimuli, but can persist in signaling location when the stimuli are removed or lights are turned off (memory fields). In this thesis, computational models of spatial information processing simulated many of the defining properties of hippocampal place cells, including memory fields. Furthermore, the models suggested a neurally plausible mechanism of goal directed spatial navigation which involved the encoding of distances in the connections between place cells. To navigate using memory fields, the models required an excitatory, distributed, and plastic association system among place cells. Such properties are well characterized in area CA3 of the hippocampus. In this thesis, a new electrophysiological study provides evidence that a second system in the dentate gyrus has similar properties. Thus, two circuits in the hippocampus meet the requirements of the models. Some predictions of the models were then tested in a single-unit recording experiment in behaving rats. Place fields were more likely to occur in information rich areas of the environment, and removal of single cues altered place fields in a way consistent with the distance encoding mechanism suggested by the models. It was concluded that a distance encoding theory of rat spatial navigation has much descriptive and predictive utility, but most of its predic

Thesis (M.Comp.Sc.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 140-157.

No description available.

A manutenção do equilíbrio depende da ativação sinérgica de músculos dos dois hemicorpos, e há evidências de que essa coordenação é mediada por circuitos medulares, que estão sob controle supra-segmentar. O objetivo desse trabalho é descrever mecanismos neurofisiológicos e biomecânicos envolvidos no controle postural de sujeitos saudáveis frente a uma perturbação provocada por uma contração reflexa, enfatizando-se os mecanismos associados à coordenação entre membros. A perturbação postural ocorreu em resposta a um estímulo elétrico unilateral no nervo tibial. Devido a restrições em estudos anteriores, utilizou-se uma ampla abordagem (múltiplos músculos, reflexos cruzados) e estimulação precisamente controlada. Os resultados mostraram um complexo padrão de ativação dos músculos dos membros inferiores bilateralmente. Logo após o estímulo, foram encontradas respostas de curta e média latência em músculos da perna e da coxa. Posteriormente, foram observadas algumas ações musculares de longa latência nos músculos mais distais, que provavelmente foram ativadas em resposta às oscilações posturais. As respostas musculares iniciais sugerem que as informações aferentes e os reflexos medulares possuem uma função muito importante na regulação da coordenação entre membros, durante a manutenção da postura ereta quieta. / Balance depends on the synergic activation of muscles bilaterally, and there is evidence that this coordination is mediated by spinal circuits, which are under supra-spinal control. The objective of this study is to describe neurophysiologic and biomechanical mechanisms involved in the postural control of healthy subjects submitted to a disturbance provoked by a muscular reflex contraction. The postural perturbation was caused by a unilateral electric stimulation to the popliteal fossa. The analysis emphasizes the mechanisms associated with interlimb coordination. In this work, methodological approaches expanded those of previous work, the recordings being done bilaterally and the stimulus being precisely controlled. The results showed a complex pattern of bilateral muscular activation. Short and medium latency responses were found in the leg and thigh muscles. These were followed by some muscular activity at longer latencies, probably occurring due to the postural oscillations. The initial muscular responses suggest that the afferent inflow and the spinal cord reflexes have an important function in the between-limb coordination during the standing posture.

A percepção de movimento é uma característica essencial à sobrevivência de diversas espécies. Na natureza, é através do movimento que uma presa percebe a chegada de um predador e decide em que direção deve fugir, bem como o predador detecta a presença de uma presa e decide para onde atacar. O Sistema Visual Humano é mais sensível a movimento do que a imagens estáticas, sendo capaz de separar as informações de movimento originadas pela movimentação própria das informações de movimento de objetos animados no ambiente. A Teoria Ecológica de Gibson (1979) provê uma base para o entendimento de como esse processo de percepção ocorre e estende-se com o conceito do que chamamos de campo vetorial de Fluxo Ótico, através do qual se representa computacionalmente o movimento. O objetivo principal deste trabalho é procurar reproduzir computacionalmente esse comportamento, para possíveis aplicações em navegação autônoma e processamento de vídeo com movimentação desconhecida. Para isso, vale-se das técnicas de estimação de Fluxo Ótico presentes na literatura, tais como as propostas por Lucas e Kanade (1981) e Farneback (1994). Em primeiro momento, avalia-se a possibilidade de utilização de uma técnica estatística de separação cega de fontes, a chamada Análise de Componentes Independentes, tomando como base o trabalho de Bell e Sejnowski (1997), na qual se mostra que tal análise aplicada em imagens fornece filtros de bordas. Depois, avalia-se a utilização do Foco de Expansão para movimentos translacionais. Resultados experimentais demonstram uma maior viabilidade da abordagem por Foco de Expansão. / Motion Perception is an essential feature for the survival of several species. In nature, it is through motion that a prey perceives the predator and is able to decide which direction to escape, and the predator detects the presence of a prey and decides where to attack. The Human Visual System is more sensitive to motion than to static imagery, and it is able to separate motion information due to egomotion from that due to an animated object in the environment. The Ecological Theory of Gibson (1979) provides a basis for understanding how this processes of perception occurs, and leads to the concept of what we call the vector field of Optical Flow, through which computational motion is represented. The main objective of this work is to try to reproduce computationally this behaviour, for possible applications in autonomous navigation and video processing with unknown self-motion. For this, we use some Optical Flow estimation techniques, as those proposed by Lucas and Kanade (1981) and Farneback (1994). At first, we assess the possibility of using a statistical technique of blind source separation, the so-called Independent Component Analysis, based on the work of Bell and Sejnowski (1997), which demonstrates that this technique, when applied to imagery, provides edge filters. Then, we assess the use of the Focus of Expansion to translational motion. Experimental results show the second approach, using the Focus of Expansion, is more viable than through Independent Component Analysis.

A percepção de movimento é uma característica essencial à sobrevivência de diversas espécies. Na natureza, é através do movimento que uma presa percebe a chegada de um predador e decide em que direção deve fugir, bem como o predador detecta a presença de uma presa e decide para onde atacar. O Sistema Visual Humano é mais sensível a movimento do que a imagens estáticas, sendo capaz de separar as informações de movimento originadas pela movimentação própria das informações de movimento de objetos animados no ambiente. A Teoria Ecológica de Gibson (1979) provê uma base para o entendimento de como esse processo de percepção ocorre e estende-se com o conceito do que chamamos de campo vetorial de Fluxo Ótico, através do qual se representa computacionalmente o movimento. O objetivo principal deste trabalho é procurar reproduzir computacionalmente esse comportamento, para possíveis aplicações em navegação autônoma e processamento de vídeo com movimentação desconhecida. Para isso, vale-se das técnicas de estimação de Fluxo Ótico presentes na literatura, tais como as propostas por Lucas e Kanade (1981) e Farneback (1994). Em primeiro momento, avalia-se a possibilidade de utilização de uma técnica estatística de separação cega de fontes, a chamada Análise de Componentes Independentes, tomando como base o trabalho de Bell e Sejnowski (1997), na qual se mostra que tal análise aplicada em imagens fornece filtros de bordas. Depois, avalia-se a utilização do Foco de Expansão para movimentos translacionais. Resultados experimentais demonstram uma maior viabilidade da abordagem por Foco de Expansão. / Motion Perception is an essential feature for the survival of several species. In nature, it is through motion that a prey perceives the predator and is able to decide which direction to escape, and the predator detects the presence of a prey and decides where to attack. The Human Visual System is more sensitive to motion than to static imagery, and it is able to separate motion information due to egomotion from that due to an animated object in the environment. The Ecological Theory of Gibson (1979) provides a basis for understanding how this processes of perception occurs, and leads to the concept of what we call the vector field of Optical Flow, through which computational motion is represented. The main objective of this work is to try to reproduce computationally this behaviour, for possible applications in autonomous navigation and video processing with unknown self-motion. For this, we use some Optical Flow estimation techniques, as those proposed by Lucas and Kanade (1981) and Farneback (1994). At first, we assess the possibility of using a statistical technique of blind source separation, the so-called Independent Component Analysis, based on the work of Bell and Sejnowski (1997), which demonstrates that this technique, when applied to imagery, provides edge filters. Then, we assess the use of the Focus of Expansion to translational motion. Experimental results show the second approach, using the Focus of Expansion, is more viable than through Independent Component Analysis.

A manutenção do equilíbrio depende da ativação sinérgica de músculos dos dois hemicorpos, e há evidências de que essa coordenação é mediada por circuitos medulares, que estão sob controle supra-segmentar. O objetivo desse trabalho é descrever mecanismos neurofisiológicos e biomecânicos envolvidos no controle postural de sujeitos saudáveis frente a uma perturbação provocada por uma contração reflexa, enfatizando-se os mecanismos associados à coordenação entre membros. A perturbação postural ocorreu em resposta a um estímulo elétrico unilateral no nervo tibial. Devido a restrições em estudos anteriores, utilizou-se uma ampla abordagem (múltiplos músculos, reflexos cruzados) e estimulação precisamente controlada. Os resultados mostraram um complexo padrão de ativação dos músculos dos membros inferiores bilateralmente. Logo após o estímulo, foram encontradas respostas de curta e média latência em músculos da perna e da coxa. Posteriormente, foram observadas algumas ações musculares de longa latência nos músculos mais distais, que provavelmente foram ativadas em resposta às oscilações posturais. As respostas musculares iniciais sugerem que as informações aferentes e os reflexos medulares possuem uma função muito importante na regulação da coordenação entre membros, durante a manutenção da postura ereta quieta. / Balance depends on the synergic activation of muscles bilaterally, and there is evidence that this coordination is mediated by spinal circuits, which are under supra-spinal control. The objective of this study is to describe neurophysiologic and biomechanical mechanisms involved in the postural control of healthy subjects submitted to a disturbance provoked by a muscular reflex contraction. The postural perturbation was caused by a unilateral electric stimulation to the popliteal fossa. The analysis emphasizes the mechanisms associated with interlimb coordination. In this work, methodological approaches expanded those of previous work, the recordings being done bilaterally and the stimulus being precisely controlled. The results showed a complex pattern of bilateral muscular activation. Short and medium latency responses were found in the leg and thigh muscles. These were followed by some muscular activity at longer latencies, probably occurring due to the postural oscillations. The initial muscular responses suggest that the afferent inflow and the spinal cord reflexes have an important function in the between-limb coordination during the standing posture.