No description available.

Flow is a mental state characterised by a feeling of energised focus, complete involvement and success when fully immersed in an activity. The dimensions of and the conditions required for flow to occur have been explored in a broad spectrum of situational contexts. The close relationship between flow and peak performance sparked an interest in ways to induce flow. However, any process of flow induction requires a measure to trace the degree to which flow is in fact occurring. Self-reports of the flow experience are subjective and provide ad hoc information. Psycho-physiological measures, such as EEG, can provide objective and continuous indications of the degree to which flow is occurring. Unfortunately few studies have explored the relationships between psycho-physiological measures and flow. The present study was an attempt to determine the EEG correlates of flow under conditions of peak performance. Twenty participants were asked to perform a continuous visuomotor task 10 times. Time taken per task was used as an indicator of task performance. EEG recordings were done concurrently. Participants completed an Abbreviated Flow Questionnaire (AFQ) after each task and a Game Flow Inventory (GFI) after having finished all 10 tasks. On completion, performance times and associated flow scores were standardised where after the sample was segmented into a high flow - peak performance and a low flow - low performance level. Multi-variate analysis of variance (MANOVA) was conducted on the performance, flow and EEG data to establish that a significant difference existed between the two levels. In addition, a one-way analysis of variance between high and low flow data was conducted for all variables and main effects were established. Inter-correlations of all EEG data at both levels were then conducted across four brain sites (F3, C3, P3, O1). In high flow only, results indicated increased lobeta power in the sensorimotor cortex together with a unique EEG pattern showing beta band synchronisation between the prefrontal and sensori-motor areas and de-synchronisation between all other areas, while all other frequencies (delta, theta, alpha, lobeta, hibeta, and gamma) remained synchronised across all scalp locations. These findings supported a theoretical neuropsychological model of flow. / Psychology / D. Com. (Consulting Psychology)

La naissance prématurée se caractérise par des expériences multisensorielles et sensorimotrices atypiques lors d’une période du développement très sensible à ces dernières (Koenig-Zores & Kuhn, 2016). Les recherches ont mis en évidence un impact significatif de la prématurité sur le développement des enfants (Marret et al., 2015) induisant notamment des troubles perceptivo-moteurs avec ou sans troubles neurologiques associés (De Rose et al., 2013). Cependant, si beaucoup d’études portent sur la motricité des nouveau-nés et nourrissons nés prématurés, peu de données existent sur le développement perceptivo-moteur des enfants nés prématurés sans diagnostic de trouble neurodéveloppemental. La question principale abordée dans cette thèse est de savoir si la prématurité n’induit pas des signatures motrices spécifiques, même en absence de ces troubles. Dans l’objectif de répondre à cette question, différents tests standardisés, et trois tâches expérimentales impliquant la perception des équivalences intermodalitaires, la coordination visuomotrice et le contrôle postural, ont été proposés à 48 enfants nés à terme et 32 enfants nés grands prématurés sans diagnostic de trouble neurodéveloppemental et tous âgés de 8 ans. Les résultats ont mis en évidence dans les deux groupes des habiletés comparables de perception des équivalences intermodalitaires dans les modalités haptique et visuelle. Cependant, ils ont aussi révélé une efficience moindre de la coordination visuomotrice et du contrôle postural chez les enfants nés prématurés en comparaison des enfants nés à terme. Ces différences suggèrent des processus perceptivo-moteurs différents chez les enfants nés grands prématurés sans diagnostic de trouble neurodéveloppemental âgés de 8 ans. Ces résultats offrent ainsi de nouvelles perspectives cliniques, notamment d’évaluation plus fine des habiletés perceptivo-motrices, ainsi que de nouveaux questionnements de recherche sur les trajectoires développementales de ces mêmes habiletés et des réseaux neuronaux sous-jacents chez les enfants nés prématurés. / Preterm birth is associated with atypical multisensory and sensorimotor experiences during a period of development sensitive to these experiences (Koenig-Zores & Kuhn, 2016). The studies showed a significant impact of prematurity on children development (Marret et al., 2015), such as perceptual-motor disorders, with or without associated neurological disorders (De Rose et al., 2013). However, even though there are many studies on motor abilities of preterm newborns and preterm infants, little data exists on perceptual-motor development of preterm children without neurodevelopmental disorders. The main question addressed in this thesis is to know whether prematurity does induce specific motor signatures, even in the absence of neurodevelopmental disorders. To answer this question, different standardized tests and three research tasks involving perception of intersensory equivalences, visuomotor coordination, and postural control, have been proposed to 48 full-term children and 32 very preterm children without any diagnosis of neurodevelopmental disorders, all aged 8 years old. The results revealed comparable perception abilities of intersensory equivalences in haptic and visual modalities in the preterm and the full-term groups. However, they also showed a lower efficiency of visuomotor coordination and postural control in the preterm children compared to the full-term children. These observations suggest different perceptual-motor processes in very preterm children without diagnosis of neurodevelopmental disorders at the age of 8. The results offer new clinical opportunities for a more precise evaluation of perceptual-motor abilities, and new research questions about developmental trajectories of perceptual-motor abilities and underlying neuronal networks, in preterm children.

L’intégrité de notre système sensorimoteur est essentielle aux interactions adéquates avec notre environnement. Dans la maladie de Parkinson (MP), l’efficacité des interactions quotidiennes entre le corps et l’environnement est fréquemment réduite et diminue la qualité de vie. La MP est une maladie neurodégénérative résultant prioritairement d’une perte neuronale dopaminergique dans les ganglions de la base (GB). Cette dégénérescence altère le fonctionnement normal de la circuiterie associant les GB au cortex cérébral. L’administration de médications dopaminergiques permet d’améliorer les principaux symptômes cliniques moteurs de la MP. Cette thèse porte sur les rôles des GB dans les processus de traitement et d’intégration des informations sensorielles visuelle et proprioceptive et dans les mécanismes d’adaptation visuomotrice. Elle s’intéresse également à l’influence de la médication dopaminergique sur ces fonctions sensorimotrices. Nous avons réalisé trois études comportementales, utilisant l’atteinte manuelle tridimensionnelle comme modèle expérimental. Dans chacune de ces études, nous avons comparé la performance de personnes âgées en santé à celle de personnes souffrant de la MP avec et sans leur médication antiparkinsonienne quotidienne. Ces trois études ont été réalisées à l’aide d’un système d’analyse de mouvement et une station de réalité virtuelle. Dans la première étude, nous avons évalué si les GB sont prioritairement impliqués dans l’intégration sensorimotrice ou le traitement des informations proprioceptives. Pour se faire, nous avons testé la capacité des patients MP à effectuer des atteintes manuelles tridimensionnelles précises dans quatre conditions variant la nature des informations sensorielles (visuelles et/ou proprioceptives) définissant la position de la main et de la cible. Les patients MP ont effectué, en moyenne, de plus grandes erreurs spatiales que les personnes en santé uniquement lorsque les informations proprioceptives étaient la seule source d’information sensorielle disponible. De plus, ces imprécisions spatiales étaient significativement plus grandes que celles des personnes en santé, seulement lorsque les patients étaient testés dans la condition médicamentée. La deuxième étude présentée dans cette thèse a permis de démontrer que les imprécisions spatiales des patients MP dans les conditions proprioceptives étaient le résultat de déficits dans l’utilisation en temps réel des informations proprioceptives pour guider les mouvements. Dans la troisième étude, nous avons évalué si les GB sont prioritairement impliqués dans les mécanismes d’adaptation visuomotrice explicite ou implicite. Pour se faire, nous avons testé les capacités adaptatives des patients MP dans deux tâches variant le décours temporel de l’application d’une perturbation visuomotrice tridimensionnelle. Dans la tâche explicite, la perturbation était introduite soudainement, produisant de grandes erreurs détectées consciemment. Dans la condition implicite, la perturbation était introduite graduellement ce qui engendrait de petites erreurs non détectables. Les résultats montrent que les patients MP dans les conditions médicamentée et non médicamentée présentent des déficits adaptatifs uniquement dans la tâche explicite. Dans l’ensemble, les résultats expérimentaux présentés dans cette thèse montrent que la médication dopaminergique n’améliore pas le traitement des afférences proprioceptives et l’adaptation visuomotrice des personnes souffrant de la MP. Ces observations suggèrent que les dysfonctions dans les circuits dopaminergiques dans les GB ne sont pas les seules responsables des déficits observés dans ces fonctions sensorimotrices. / The integrity of our sensorimotor system is essential for adequate interactions with the environment. In Parkinson’s disease (PD), the efficiency of the daily interactions between the body and the environment is often reduced and interfere with quality of life. PD is a neurodegenerative disease resulting primarily from a dopaminergic neuronal loss in the basal ganglia (BG). This progressive loss of neurons alters the normal functioning of the BG-cortical circuitry. Dopaminergic medication is well known to remediate the major clinical motor symptoms of PD. This thesis investigates the role of the BG in the processing and integration of visual and proprioceptive sensory information and in visuomotor adaptation. This thesis also explores the influence of dopaminergic medication on these sensorimotor functions. We performed three behavioral studies using three-dimensional reaching movements as an experimental model. In each study, we compared the performance of healthy controls and individuals suffering from PD, while in the non-medicated condition and when on their regular daily antiparkinsonian medication. These three studies were performed using a movement analysis system and a virtual reality station. In the first study, we evaluated whether the BG are primarily involved in sensorimotor integration or in the processing of proprioceptive sensory information. We tested the ability of PD patients to perform accurate reaching movements in four conditions in which the sensory signals defining target and hand positions (vision and/or proprioception) varied. On average, PD patients made larger spatial errors than healthy controls when proprioception was the only source of sensory information available. Furthermore, these movement inaccuracies were significantly larger than those of healthy controls only when PD patients where tested in the medicated condition. The second study presented in this thesis demonstrated that the greater movement inaccuracies of PD patients in the proprioceptive conditions resulted mainly from impaired use of proprioceptive information for on-line movement guidance. In the third study, we evaluated whether the BG are primarily involved in explicit or implicit visoumotor adaptation mechanisms. Visuomotor adaptation skills of non-medicated and medicated patients were assessed in two reaching tasks in which the size of spatial errors made during adaptation was manipulated by varying the temporal evolution of a three-dimensional visuomotor perturbation across trials. In the explicit task, the visuomotor perturbation was applied suddenly resulting in large consciously detected initial spatial errors, whereas in the implicit task, the visuomotor perturbation was gradually introduced in small undetectable steps such that subjects never experienced large movement errors. Results indicate that both non- medicated and medicated PD patients showed markedly impaired visuomotor adaptation only in the explicit task. Together, the different experimental data presented in this thesis indicate that dopaminergic medication does not improve proprioceptive processing and visuomotor adaptation skills of PD patients. These observations suggest that dysfunction of dopaminergic circuits within the BG is not solely responsible for the reported sensorimotor deficits.

Muitas das interações que temos com o ambiente envolvem situações dinâmicas. Raramente estas situações são realizadas de maneira isolada. Em ações interceptativas, por exemplo, o sistema nervoso precisa estimar quando um alvo irá atingir uma determinada posição e constantemente ajustar os movimentos para diferentes contextos. Apesar de estudos psicofísicos terem investigado possíveis variáveis ópticas e modulações do contexto envolvidas na integração visuomotora, pouca atenção foi direcionada para compreender os mecanismos cerebrais da integração de informação visual de movimento e ações motoras em cenários dinâmicos. O objetivo geral desta tese foi investigar estes mecanismos e entender como o contexto modula a atividade cerebral em ações interceptativas em adultos jovens saudáveis. No primeiro experimento, foram investigadas quais áreas estão associadas com a integração entre informação visual de movimento e ação motora sincronizatória. Foi utilizado desenho relacionado à eventos em ressonância magnética funcional avaliando a atividade cerebral em tarefa de timing coincidente. Foi identificada uma rede fronto-parietal bilateral dorsal e ativação bilateral do braço ascendente do sulco temporal inferior, região funcionalmente definida como hV5+, e giro angular. No segundo experimento, foi testada a influência causal da área hV5+ e córtex pré-motor dorsal no viés comportamental que tentativa prévia exerce sobre a tentativa atual usando estimulação magnética transcraniana. Os resultados deste experimento sugerem que o efeito da tentativa prévia depende fortemente de um mecanismo de memória de curto prazo implícito no córtex pré-motor dorsal e moderadamente da área hV5+. No terceiro experimento, o objetivo foi verificar o efeito da repetição e expectativa de repetição da velocidade do estímulo nas áreas associadas com ações interceptativas. Para isso, os participantes interceptaram pares de alvos móveis com velocidade igual ou diferente em experimento relacionado à eventos em ressonância magnética funcional. A expectativa sobre a repetição da velocidade do estímulo foi manipulada pela probabilidade de repetição da velocidade do alvo em diferentes blocos. Os resultados comportamentais indicaram que a velocidade do primeiro estímulo enviesou o erro temporal dos participantes para responder ao segundo estímulo e que a manipulação da expectativa dos participantes não resultou em diferença no erro temporal. Não houve modulação da amplitude do sinal BOLD pela repetição do estímulo ou pela manipulação da expectativa sobre a repetição de velocidade. No quarto experimento, foram investigados os mecanismos cerebrais que permitem que a expectativa influencie o comportamento em uma tarefa de timing coincidente. Para isso, a expectativa sobre a velocidade do alvo foi manipulada a cada tentativa por meio de dicas em um experimento relacionado à eventos em ressonância magnética funcional. Os resultados deste experimento mostraram que a expectativa sobre a velocidade do alvo aumenta o sinal BOLD para expectativa válida em hV5+ e córtex pré-motor dorsal. Em geral, os resultados desta tese mostram que a integração visuomotora em ações interceptativas está associada com atividade em uma rede fronto-parietal dorsal e da área hV5+. Destas áreas, foi verificado que o córtex pré-motor dorsal e área hV5+ tem papel de armazenar informação da tentativa prévia que enviesa o comportamento na tentativa atual. Por fim, foi mostrado que a expectativa sobre a velocidade do alvo modula o sinal BOLD em áreas iniciais do processamento sensorial e de planejamento motor. Estes resultados avançam o conhecimento sobre os mecanismos neurais associados à integração visuomotora em ações interceptativas e mostram como o contexto em que a tarefa é realizada modula essa integração / Many of our interactions with the environment happen in dynamic situations. These situations are rarely experienced in isolation. In interceptive actions, for example, the nervous system needs to estimate when a target will arrive at a certain position and constantly adjust movements for different contexts. Although psychophysical studies have investigated the putative optical variables and contextual modulations in visuomotor integration, less attention has been devoted to understand brain mechanisms underlying the integration of visual motion information and motor actions in dynamic scenarios. The main goal of the present thesis was to investigate the brain mechanisms involved in visuomotor integration of interceptive actions in healthy young adults. In the first experiment, it was investigated which brain areas are associated with integration of visual motion information and timed motor action in an event-related functional magnetic resonance imaging experiment. Results showed greater BOLD signal in a bilateral dorsal fronto-parietal network, as well as hV5+ and angular gyrus. In the second experiment, it was tested the causal influence of area hV5+ and dorsal premotor cortex on the behavioral bias that previous trial exerts on the current trial using transcranial magnetic stimulation. The results of this experiment provide causal evidence that the previous trial effect is mediated to a large extent by an implicit shortterm memory mechanism in the dorsal premotor cortex, and to a lesser extent by hV5 +, in a visuomotor integration task with moving objects. In the third experiment, the goal was to verify the effect of repetition and expectation about repetition of speed in brain areas associated with visuomotor integration in interceptive actions. To that end, participants intercepted pairs of moving targets with either same or different speed in an event-related functional magnetic resonance experiment. Expectation about speed repetition of target speed was manipulated through the probability of speed repetition in different blocks. Behavioral results indicate that speed from the first stimulus biased participants\' temporal error for the second stimulus. However, manipulation of participants\' expectation did not affect temporal error. In addition, BOLD signal amplitude was modulated by neither stimulus speed repetition nor expectation. In the forth experiment, brain mechanisms that allow expectation to influence behavior in a coincident timing task were investigated. Participant\'s expectation about target speed was manipulated on a trial-by-trial basis by means of cues in an event-related functional magnetic resonance experiment. The results of this experiment showed that expectation about target speed increases BOLD signal for valid expectations in hV5+ and dorsal premotor cortex. Overall, the results in this thesis show that visuomotor integration in interceptive actions is associated with activity in a dorsal fronto-parietal network and hV5+. In addition, it was verified that dorsal premotor cortex and hV5+ have a role in storing information from previous trial that bias behavior on the current trial. Lastly, it was shown that expectation about upcoming target speed modulates BOLD signal in early stage visual motion processing as well as motor planning areas. These results advance knowledge about the brain mechanisms associated with visuomotor integration in interceptive actions and show how context modulates this integration process

L’intégrité de notre système sensorimoteur est essentielle aux interactions adéquates avec notre environnement. Dans la maladie de Parkinson (MP), l’efficacité des interactions quotidiennes entre le corps et l’environnement est fréquemment réduite et diminue la qualité de vie. La MP est une maladie neurodégénérative résultant prioritairement d’une perte neuronale dopaminergique dans les ganglions de la base (GB). Cette dégénérescence altère le fonctionnement normal de la circuiterie associant les GB au cortex cérébral. L’administration de médications dopaminergiques permet d’améliorer les principaux symptômes cliniques moteurs de la MP. Cette thèse porte sur les rôles des GB dans les processus de traitement et d’intégration des informations sensorielles visuelle et proprioceptive et dans les mécanismes d’adaptation visuomotrice. Elle s’intéresse également à l’influence de la médication dopaminergique sur ces fonctions sensorimotrices. Nous avons réalisé trois études comportementales, utilisant l’atteinte manuelle tridimensionnelle comme modèle expérimental. Dans chacune de ces études, nous avons comparé la performance de personnes âgées en santé à celle de personnes souffrant de la MP avec et sans leur médication antiparkinsonienne quotidienne. Ces trois études ont été réalisées à l’aide d’un système d’analyse de mouvement et une station de réalité virtuelle. Dans la première étude, nous avons évalué si les GB sont prioritairement impliqués dans l’intégration sensorimotrice ou le traitement des informations proprioceptives. Pour se faire, nous avons testé la capacité des patients MP à effectuer des atteintes manuelles tridimensionnelles précises dans quatre conditions variant la nature des informations sensorielles (visuelles et/ou proprioceptives) définissant la position de la main et de la cible. Les patients MP ont effectué, en moyenne, de plus grandes erreurs spatiales que les personnes en santé uniquement lorsque les informations proprioceptives étaient la seule source d’information sensorielle disponible. De plus, ces imprécisions spatiales étaient significativement plus grandes que celles des personnes en santé, seulement lorsque les patients étaient testés dans la condition médicamentée. La deuxième étude présentée dans cette thèse a permis de démontrer que les imprécisions spatiales des patients MP dans les conditions proprioceptives étaient le résultat de déficits dans l’utilisation en temps réel des informations proprioceptives pour guider les mouvements. Dans la troisième étude, nous avons évalué si les GB sont prioritairement impliqués dans les mécanismes d’adaptation visuomotrice explicite ou implicite. Pour se faire, nous avons testé les capacités adaptatives des patients MP dans deux tâches variant le décours temporel de l’application d’une perturbation visuomotrice tridimensionnelle. Dans la tâche explicite, la perturbation était introduite soudainement, produisant de grandes erreurs détectées consciemment. Dans la condition implicite, la perturbation était introduite graduellement ce qui engendrait de petites erreurs non détectables. Les résultats montrent que les patients MP dans les conditions médicamentée et non médicamentée présentent des déficits adaptatifs uniquement dans la tâche explicite. Dans l’ensemble, les résultats expérimentaux présentés dans cette thèse montrent que la médication dopaminergique n’améliore pas le traitement des afférences proprioceptives et l’adaptation visuomotrice des personnes souffrant de la MP. Ces observations suggèrent que les dysfonctions dans les circuits dopaminergiques dans les GB ne sont pas les seules responsables des déficits observés dans ces fonctions sensorimotrices. / The integrity of our sensorimotor system is essential for adequate interactions with the environment. In Parkinson’s disease (PD), the efficiency of the daily interactions between the body and the environment is often reduced and interfere with quality of life. PD is a neurodegenerative disease resulting primarily from a dopaminergic neuronal loss in the basal ganglia (BG). This progressive loss of neurons alters the normal functioning of the BG-cortical circuitry. Dopaminergic medication is well known to remediate the major clinical motor symptoms of PD. This thesis investigates the role of the BG in the processing and integration of visual and proprioceptive sensory information and in visuomotor adaptation. This thesis also explores the influence of dopaminergic medication on these sensorimotor functions. We performed three behavioral studies using three-dimensional reaching movements as an experimental model. In each study, we compared the performance of healthy controls and individuals suffering from PD, while in the non-medicated condition and when on their regular daily antiparkinsonian medication. These three studies were performed using a movement analysis system and a virtual reality station. In the first study, we evaluated whether the BG are primarily involved in sensorimotor integration or in the processing of proprioceptive sensory information. We tested the ability of PD patients to perform accurate reaching movements in four conditions in which the sensory signals defining target and hand positions (vision and/or proprioception) varied. On average, PD patients made larger spatial errors than healthy controls when proprioception was the only source of sensory information available. Furthermore, these movement inaccuracies were significantly larger than those of healthy controls only when PD patients where tested in the medicated condition. The second study presented in this thesis demonstrated that the greater movement inaccuracies of PD patients in the proprioceptive conditions resulted mainly from impaired use of proprioceptive information for on-line movement guidance. In the third study, we evaluated whether the BG are primarily involved in explicit or implicit visoumotor adaptation mechanisms. Visuomotor adaptation skills of non-medicated and medicated patients were assessed in two reaching tasks in which the size of spatial errors made during adaptation was manipulated by varying the temporal evolution of a three-dimensional visuomotor perturbation across trials. In the explicit task, the visuomotor perturbation was applied suddenly resulting in large consciously detected initial spatial errors, whereas in the implicit task, the visuomotor perturbation was gradually introduced in small undetectable steps such that subjects never experienced large movement errors. Results indicate that both non- medicated and medicated PD patients showed markedly impaired visuomotor adaptation only in the explicit task. Together, the different experimental data presented in this thesis indicate that dopaminergic medication does not improve proprioceptive processing and visuomotor adaptation skills of PD patients. These observations suggest that dysfunction of dopaminergic circuits within the BG is not solely responsible for the reported sensorimotor deficits.

Muitas das interações que temos com o ambiente envolvem situações dinâmicas. Raramente estas situações são realizadas de maneira isolada. Em ações interceptativas, por exemplo, o sistema nervoso precisa estimar quando um alvo irá atingir uma determinada posição e constantemente ajustar os movimentos para diferentes contextos. Apesar de estudos psicofísicos terem investigado possíveis variáveis ópticas e modulações do contexto envolvidas na integração visuomotora, pouca atenção foi direcionada para compreender os mecanismos cerebrais da integração de informação visual de movimento e ações motoras em cenários dinâmicos. O objetivo geral desta tese foi investigar estes mecanismos e entender como o contexto modula a atividade cerebral em ações interceptativas em adultos jovens saudáveis. No primeiro experimento, foram investigadas quais áreas estão associadas com a integração entre informação visual de movimento e ação motora sincronizatória. Foi utilizado desenho relacionado à eventos em ressonância magnética funcional avaliando a atividade cerebral em tarefa de timing coincidente. Foi identificada uma rede fronto-parietal bilateral dorsal e ativação bilateral do braço ascendente do sulco temporal inferior, região funcionalmente definida como hV5+, e giro angular. No segundo experimento, foi testada a influência causal da área hV5+ e córtex pré-motor dorsal no viés comportamental que tentativa prévia exerce sobre a tentativa atual usando estimulação magnética transcraniana. Os resultados deste experimento sugerem que o efeito da tentativa prévia depende fortemente de um mecanismo de memória de curto prazo implícito no córtex pré-motor dorsal e moderadamente da área hV5+. No terceiro experimento, o objetivo foi verificar o efeito da repetição e expectativa de repetição da velocidade do estímulo nas áreas associadas com ações interceptativas. Para isso, os participantes interceptaram pares de alvos móveis com velocidade igual ou diferente em experimento relacionado à eventos em ressonância magnética funcional. A expectativa sobre a repetição da velocidade do estímulo foi manipulada pela probabilidade de repetição da velocidade do alvo em diferentes blocos. Os resultados comportamentais indicaram que a velocidade do primeiro estímulo enviesou o erro temporal dos participantes para responder ao segundo estímulo e que a manipulação da expectativa dos participantes não resultou em diferença no erro temporal. Não houve modulação da amplitude do sinal BOLD pela repetição do estímulo ou pela manipulação da expectativa sobre a repetição de velocidade. No quarto experimento, foram investigados os mecanismos cerebrais que permitem que a expectativa influencie o comportamento em uma tarefa de timing coincidente. Para isso, a expectativa sobre a velocidade do alvo foi manipulada a cada tentativa por meio de dicas em um experimento relacionado à eventos em ressonância magnética funcional. Os resultados deste experimento mostraram que a expectativa sobre a velocidade do alvo aumenta o sinal BOLD para expectativa válida em hV5+ e córtex pré-motor dorsal. Em geral, os resultados desta tese mostram que a integração visuomotora em ações interceptativas está associada com atividade em uma rede fronto-parietal dorsal e da área hV5+. Destas áreas, foi verificado que o córtex pré-motor dorsal e área hV5+ tem papel de armazenar informação da tentativa prévia que enviesa o comportamento na tentativa atual. Por fim, foi mostrado que a expectativa sobre a velocidade do alvo modula o sinal BOLD em áreas iniciais do processamento sensorial e de planejamento motor. Estes resultados avançam o conhecimento sobre os mecanismos neurais associados à integração visuomotora em ações interceptativas e mostram como o contexto em que a tarefa é realizada modula essa integração / Many of our interactions with the environment happen in dynamic situations. These situations are rarely experienced in isolation. In interceptive actions, for example, the nervous system needs to estimate when a target will arrive at a certain position and constantly adjust movements for different contexts. Although psychophysical studies have investigated the putative optical variables and contextual modulations in visuomotor integration, less attention has been devoted to understand brain mechanisms underlying the integration of visual motion information and motor actions in dynamic scenarios. The main goal of the present thesis was to investigate the brain mechanisms involved in visuomotor integration of interceptive actions in healthy young adults. In the first experiment, it was investigated which brain areas are associated with integration of visual motion information and timed motor action in an event-related functional magnetic resonance imaging experiment. Results showed greater BOLD signal in a bilateral dorsal fronto-parietal network, as well as hV5+ and angular gyrus. In the second experiment, it was tested the causal influence of area hV5+ and dorsal premotor cortex on the behavioral bias that previous trial exerts on the current trial using transcranial magnetic stimulation. The results of this experiment provide causal evidence that the previous trial effect is mediated to a large extent by an implicit shortterm memory mechanism in the dorsal premotor cortex, and to a lesser extent by hV5 +, in a visuomotor integration task with moving objects. In the third experiment, the goal was to verify the effect of repetition and expectation about repetition of speed in brain areas associated with visuomotor integration in interceptive actions. To that end, participants intercepted pairs of moving targets with either same or different speed in an event-related functional magnetic resonance experiment. Expectation about speed repetition of target speed was manipulated through the probability of speed repetition in different blocks. Behavioral results indicate that speed from the first stimulus biased participants\' temporal error for the second stimulus. However, manipulation of participants\' expectation did not affect temporal error. In addition, BOLD signal amplitude was modulated by neither stimulus speed repetition nor expectation. In the forth experiment, brain mechanisms that allow expectation to influence behavior in a coincident timing task were investigated. Participant\'s expectation about target speed was manipulated on a trial-by-trial basis by means of cues in an event-related functional magnetic resonance experiment. The results of this experiment showed that expectation about target speed increases BOLD signal for valid expectations in hV5+ and dorsal premotor cortex. Overall, the results in this thesis show that visuomotor integration in interceptive actions is associated with activity in a dorsal fronto-parietal network and hV5+. In addition, it was verified that dorsal premotor cortex and hV5+ have a role in storing information from previous trial that bias behavior on the current trial. Lastly, it was shown that expectation about upcoming target speed modulates BOLD signal in early stage visual motion processing as well as motor planning areas. These results advance knowledge about the brain mechanisms associated with visuomotor integration in interceptive actions and show how context modulates this integration process

La locomotion est une composante fondamentale de la vie animale : elle permet l’accès continu aux ressources nécessaires à la survie ainsi que l’évitement de périls variés. Les milieux naturels comme anthropiques regorgent toutefois d’obstacles s’élevant contre notre progression. Pour l’humain et les autres mammifères terrestres naviguant principalement par la vision, le franchissement efficace de ces obstacles repose critiquement sur la capacité de modifier proactivement le positionnement et la trajectoire des pas en fonction des informations visuelles extraites durant leur approche. Au niveau du système nerveux, cette capacité implique un processus complexe où le traitement des signaux visuels reflétant les paramètres de l’obstacle spécifie un cours d’action sécurisant son franchissement, lequel est ultimement exécuté par des altérations précises à l’activité musculaire. Des études approfondies chez le chat, l’un des modèles animaux les plus développés et investigués vis-à-vis du contrôle locomoteur, ont présentement impliqué deux structures corticales dans ce processus. Le cortex pariétal postérieur contribuerait ainsi à déterminer la position relative de l’obstacle et le cortex moteur primaire serait central à l’exécution des modifications de la démarche. Cependant, notre compréhension du substrat neural impliqué dans la transformation sensorimotrice joignant ces deux étapes est extrêmement limitée. Plusieurs lignes d’évidences, particulièrement dérivées de travaux chez le primate investiguant le contrôle des mouvements volontaires du bras, pointent cependant vers une contribution potentiellement majeure du cortex prémoteur à cette fonction. Cette thèse entreprend de déterminer directement la contribution prémotrice aux modifications de la démarche. Deux études rapportent ainsi l’activité de neurones individuels enregistrés dans deux larges subdivisions du cortex prémoteur, les aires 6iffu et 4delta, chez le chat éveillé accomplissant librement une tâche de négociation d’obstacles sur tapis roulant. Ces études font état de changements d’activité distincts d’une subdivision à l’autre et corrélés à des aspects spécifiques de la tâche, incluant des changements préparatoires liés à l’approche finale de l’obstacle et d’autres liés à une ou plusieurs étapes des ajustements locomoteurs séquentiels entourant sa négociation. Une troisième étude investigue par microstimulation intracorticale la capacité des différentes subdivisions prémotrices du chat à modifier la démarche. Cette étude expose une variété de réponses électromyographiques complexes s’intégrant en phase avec la marche, où plusieurs subdivisions présentent des signatures distinctes d’effets multi-membres contrastant avec l’influence focale du cortex moteur primaire. Chacune de ces trois études est finalement complémentée d’investigations par traçage rétrograde de connexions anatomiques décisives à l’interprétation fonctionnelle des subdivisions investiguées. Ensemble, ces travaux soutiennent et précisent une contribution centrale du cortex prémoteur aux modifications de la démarche sous guidage visuel. D’une part, ils rapportent pour la première fois que l’activité neuronale de multiples subdivisions du cortex prémoteur reflète différentes étapes de la planification locomotrice stipulant les altérations à entreprendre à l’approche d’un obstacle et durant son franchissement. D’autre part, ils révèlent complémentairement que l’activation de ces subdivisions a le pouvoir d’influencer profondément la marche. Les données collectées soulignent finalement plusieurs points de comparaison entre les aires prémotrices du chat et du primate, suggérant un degré d’analogie fonctionnelle extensible à la locomotion humaine. / Locomotion is a fundamental component of animal life: it provides continuous access to the resources necessary for survival as well as the means to elude potential perils. However, both natural and built environments teem with obstacles impeding one’s progress. For humans and other terrestrial mammals navigating primarily through vision, efficiently negotiating these obstacles critically requires the capacity to proactively adapt the positioning and trajectory of each step on the basis of visual information extracted during their approach. In the nervous system, this capacity involves a complex process through which the integration of visual signals reflecting the parameters and location of an obstacle specifies a course of action to ensure its negotiation, Extensive studies in the cat, one of the most common models used to study the neural mechanisms involved in the control of locomotion, have currently implicated two cortical structures to this process. The posterior parietal cortex is suggested to contribute to the determination of the obstacle’s relative position (with respect to the body) while the primary motor cortex is central to the execution of the gait modifications. However, our comprehension of the neural substrate implicated in the sensorimotor transformation linking these defined stages is extremely limited. Several lines of evidence, predominantly derived from work in the primate investigating the voluntary control of arm movements, nonetheless point towards a potentially major contribution of the premotor cortex to this function. This thesis sets out to directly determine the premotor contribution to the control of gait modifications. Two studies report the activity of individual neurons recorded in two large subdivisions of premotor cortex, areas 6iffu and 4delta, in awake cats freely performing an obstacle negotiation task on treadmill. These studies describe distinct changes in activity across subdivisions that correlate with specific aspects of the task, including preparatory changes related to the final approach of the obstacle and others related to one or more stages of the sequential locomotor adjustments surrounding its negotiation. A third study used intracortical microstimulation to investigate the capacity of different premotor subdivisions of the cat to modify gait. This study reveals a variety of complex electromyographic responses that are integrated into the gait cycle. Moreover, several subdivisions show distinct signatures of multi-limb effects that contrast with the focal influence of the primary motor cortex. Each of these three studies is finally complemented by retrograde tracing investigations of anatomical connections critical to the functional interpretation of the subdivisions examined. Together, these studies support and clarify a central contribution of the premotor cortex to the modification of gait under visual guidance. We report for the first time that the neural activity of multiple subdivisions of the premotor cortex reflects different stages of the locomotor plan specifying the gait alterations to perform during the approach and crossing of an obstacle. In addition, we reveal that activation of these subdivisions has the power to profoundly influence walking. The data collected finally highlight several points of comparison between the premotor areas of the cat and the primate, suggesting a degree of functional analogy extensible to human locomotion.

Le traumatisme craniocérébral léger (TCCL) a des effets complexes sur plusieurs fonctions cérébrales, dont l’évaluation et le suivi peuvent être difficiles. Les problèmes visuels et les troubles de l’équilibre font partie des plaintes fréquemment rencontrées après un TCCL. En outre, ces problèmes peuvent continuer à affecter les personnes ayant eu un TCCL longtemps après la phase aiguë du traumatisme. Cependant, les évaluations cliniques conventionnelles de la vision et de l’équilibre ne permettent pas, la plupart du temps, d’objectiver ces symptômes, surtout lorsqu’ils s’installent durablement. De plus, il n’existe pas, à notre connaissance, d’étude longitudinale ayant étudié les déficits visuels perceptifs, en tant que tels, ni les troubles de l’équilibre secondaires à un TCCL, chez l’adulte. L’objectif de ce projet était donc de déterminer la nature et la durée des effets d’un tel traumatisme sur la perception visuelle et sur la stabilité posturale, en évaluant des adultes TCCL et contrôles sur une période d’un an. Les mêmes sujets, exactement, ont participé aux deux expériences, qui ont été menées les mêmes jours pour chacun des sujets. L’impact du TCCL sur la perception visuelle de réseaux sinusoïdaux définis par des attributs de premier et de second ordre a d’abord été étudié. Quinze adultes diagnostiqués TCCL ont été évalués 15 jours, 3 mois et 12 mois après leur traumatisme. Quinze adultes contrôles appariés ont été évalués à des périodes identiques. Des temps de réaction (TR) de détection de clignotement et de discrimination de direction de mouvement ont été mesurés. Les niveaux de contraste des stimuli de premier et de second ordre ont été ajustés pour qu’ils aient une visibilité comparable, et les moyennes, médianes, écarts-types (ET) et écarts interquartiles (EIQ) des TR correspondant aux bonnes réponses ont été calculés. Le niveau de symptômes a également été évalué pour le comparer aux données de TR. De façon générale, les TR des TCCL étaient plus longs et plus variables (plus grands ET et EIQ) que ceux des contrôles. De plus, les TR des TCCL étaient plus courts pour les stimuli de premier ordre que pour ceux de second ordre, et plus variables pour les stimuli de premier ordre que pour ceux de second ordre, dans la condition de discrimination de mouvement. Ces observations se sont répétées au cours des trois sessions. Le niveau de symptômes des TCCL était supérieur à celui des participants contrôles, et malgré une amélioration, cet écart est resté significatif sur la période d’un an qui a suivi le traumatisme. La seconde expérience, elle, était destinée à évaluer l’impact du TCCL sur le contrôle postural. Pour cela, nous avons mesuré l’amplitude d’oscillation posturale dans l’axe antéropostérieur et l’instabilité posturale (au moyen de la vitesse quadratique moyenne (VQM) des oscillations posturales) en position debout, les pieds joints, sur une surface ferme, dans cinq conditions différentes : les yeux fermés, et dans un tunnel virtuel tridimensionnel soit statique, soit oscillant de façon sinusoïdale dans la direction antéropostérieure à trois vitesses différentes. Des mesures d’équilibre dérivées de tests cliniques, le Bruininks-Oseretsky Test of Motor Proficiency 2nd edition (BOT-2) et le Balance Error Scoring System (BESS) ont également été utilisées. Les participants diagnostiqués TCCL présentaient une plus grande instabilité posturale (une plus grande VQM des oscillations posturales) que les participants contrôles 2 semaines et 3 mois après le traumatisme, toutes conditions confondues. Ces troubles de l’équilibre secondaires au TCCL n’étaient plus présents un an après le traumatisme. Ces résultats suggèrent également que les déficits affectant les processus d’intégration visuelle mis en évidence dans la première expérience ont pu contribuer aux troubles de l’équilibre secondaires au TCCL. L’amplitude d’oscillation posturale dans l’axe antéropostérieur de même que les mesures dérivées des tests cliniques d’évaluation de l’équilibre (BOT-2 et BESS) ne se sont pas révélées être des mesures sensibles pour quantifier le déficit postural chez les sujets TCCL. L’association des mesures de TR à la perception des propriétés spécifiques des stimuli s’est révélée être à la fois une méthode de mesure particulièrement sensible aux anomalies visuomotrices secondaires à un TCCL, et un outil précis d’investigation des mécanismes sous-jacents à ces anomalies qui surviennent lorsque le cerveau est exposé à un traumatisme léger. De la même façon, les mesures d’instabilité posturale se sont révélées suffisamment sensibles pour permettre de mesurer les troubles de l’équilibre secondaires à un TCCL. Ainsi, le développement de tests de dépistage basés sur ces résultats et destinés à l’évaluation du TCCL dès ses premières étapes apparaît particulièrement intéressant. Il semble également primordial d’examiner les relations entre de tels déficits et la réalisation d’activités de la vie quotidienne, telles que les activités scolaires, professionnelles ou sportives, pour déterminer les impacts fonctionnels que peuvent avoir ces troubles des fonctions visuomotrice et du contrôle de l’équilibre. / Mild traumatic brain injury (mTBI) has complex effects on several brain functions that can be difficult to assess and follow-up. Visual and balance problems are frequently reported after an mTBI. Furthermore, these problems can still affect mTBI individuals far beyond the acute stage of injury. However, standard clinical assessments of vision and balance most often fail to objectivize these symptoms, especially if they are lingering. Moreover, to our knowledge, no longitudinal study investigated either mTBI-related deficits of visual perception per se, or mTBI-related balance deficits in adults. The aim of this project was to determine the nature and duration of the effects of such a traumatism on visual perception as well as on postural stability, by evaluating mTBI and control adults over a one-year period. Exactly the same subjects participated in both experiments, which took place on the same days for every subject. The impact of mTBI on the visual perception of sine-wave gratings defined by first-and second-order characteristics was, first, investigated. Fifteen adults diagnosed with mTBI were assessed at 15 days, 3 months and 12 months after injury. Fifteen matched controls followed the same testing schedule. Reaction times (RTs) for flicker detection and motion direction discrimination were measured. Stimulus contrast of first- and second-order patterns was equated to control for visibility, and correct-response RT means, standard deviations (SDs), medians, and interquartile ranges (IQRs) were calculated. The level of symptoms was also evaluated to compare it to RT data. In general in mTBI, RTs were longer and more variable (ie., larger SDs and IQRs), than those of controls. In addition, mTBI participants’ RTs to first-order stimuli were shorter than those to second-order stimuli, and more irregular for first- than for second-order stimuli in the motion condition. All these observations were made over the 3 sessions. The level of symptoms observed in mTBI was higher than that of control participants and this difference did also persist up to one year after the brain injury, despite an improvement. The second experiment, then, investigated the impact of mTBI on postural control. To achieve that, antero-posterior body sway amplitude (BSA) and postural instability (given by body sway velocity root mean square, vRMS) during upright stance, feet together, on a firm surface, were measured in five different conditions: with eyes closed and in a 3D virtual reality tunnel, either static or sinusoidally moving in the antero-posterior direction at 3 different velocities. Balance measures derived from clinical tests, Bruininks-Oseretsky Test of Motor Proficiency 2nd edition (BOT-2) and Balance Error Scoring System (BESS), were also used. Participants diagnosed with mTBI exhibited more postural instability (i.e. higher body sway vRMS) than control participants at 2 weeks and at 3 months post-injury, regardless of the testing condition. These mTBI-related balance deficits were no longer present one year postinjury. These results also suggest that visual processing impairments revealed in the first experiment might have contributed to mTBI-related balance deficits. Anteroposterior BSA as well as measures derived from clinical tests for balance assessment did not appear to be sensitive enough to quantify postural deficits of mTBI participants. The combination of RT measures with particular stimulus properties appeared to be a highly sensitive method for measuring mTBI-induced visuomotor anomalies, and to provide a fine probe of the underlying mechanisms when the brain is exposed to mild trauma. Likewise, postural instability measures prove to be sensitive enough for measuring mTBI-induced balance deficits. Developing screening tests in this respect intended for early post-mTBI use would be of interest. Also, studying relationships of such deficits with performance in daily life activities, such as school, work, or sports, is crucial in order to determine the functional impacts of these alterations in visuomotor and balance functions.

A wide literature of predominantly behavioural experiments that use Stimulus Response Compatibility (SRC) have suggested that visual action information such as object affordance yields rapid and concurrent activation of visual and motor brain areas, but has rarely provided direct evidence for this proposition. This thesis examines some of the key claims from the affordance literature by applying electrophysiological measures to well established SRC procedures to determine the verities of the behavioural claims of rapid and automatic visuomotor activation evoked by viewing affording objects. The temporal sensitivity offered by the Lateralised Readiness Potential and by visual evoked potentials P1 and N1 made ideal candidates to assess the behavioural claims of rapid visuomotor activation by seen objects by examining the timecourse of neural activation elicited by viewing affording objects under various conditions. The experimental work in this thesis broadly confirms the claims of the behavioural literature however it also found a series of novel results that are not predicted by the behavioural literature due to limitations in reaction time measures. For example, while different classes of affordance have been shown to exert the same behavioural facilitation, electrophysiological measures reveal very different patterns of cortical activation for grip-type and lateralised affordances. These novel findings question the applicability of the label ‘visuomotor’ to grip-type affordance processing and suggest considerable revision to models of affordance. This thesis also offers a series of novel and surprising insights into the ability to dissociate afforded motor activity from behavioural output, into the relationship between affordance and early visual evoked potentials, and into affordance in the absence of the intention to act. Overall, this thesis provides detailed suggestions for considerable changes to current models of the neural activity underpinning object affordance.