Movement and memory are two of the most fundamental components of our existence. From the moment of birth, we rely on a variety of movements to interact with people and objects around us, and as we grow, we continuously form new motor memories to improve the fidelity of these interactions by exploring and learning more about our environment, especially in unfamiliar situations, ultimately becoming better equipped to handle novel and unknown environments. In this dissertation, we explore four facets of motor memory associated with voluntary movement and postural control in the upper limbs: (1) Optimal motor memory formation via sensorimotor integration. We ask whether the motor system combines prior memories with new sensory information to produce statistically-optimal weight estimates. We find that the weight estimate that the motor system makes in order to re-stabilize one’s arm posture when an object is rapidly removed from the hand that supports it, reflected information integration in a Bayesian, statistically-optimal fashion. Remarkably, we demonstrate that when experiencing the well-known size-weight illusion, the motor and perceptual system’s weight estimates are biased in opposite directions, suggesting two divergent modes for information integration within the central nervous system. (2) Movement features important for the learning and generalization of motor memories. We show that, velocity-dependent adaptation generalizes across different movements, even from discrete straight point-to-point to continuous circular movements, however the amount of generalization is limited and context-dependent. In a series of experiments, we quantified the contributions of different movement features to the elicited adaptation transfer. In particular, we show that other movement states (i.e. position and acceleration) make only minor contributions whereas, the contexts provided by movement geometry and movement continuity are critical. (3) Internal representation of motor memories in intrinsic-extrinsic coordinates. We show that motor memories are based not on fully intrinsic or extrinsic representations but on a gain-field (multiplicative) combination the two. This gain-field representation generalizes between actions by effectively computing movement similarity based on the Mahalanobis distance across both intrinsic and extrinsic coordinates, in line with neural recordings showing mixed intrinsic-extrinsic representations in motor and parietal cortices. (4) Motor memories with local and global generalization. We demonstrate the existence of two distinct components of motor memory displaying different generalization footprints: One generalizes only locally, around the trained movement direction and with the trained end-effector, whereas the other generalizes broadly across both., We proceed to show that broad generalization results from a rapidly-learning adaptive process, dominates on easier-to-learn tasks, and performs high-level processing, producing adaptation vectors that integrate multiple sources of information, in line with a recent theory for perceptual learning. / Engineering and Applied Sciences

Quel rôle joue la gravité dans les représentations internes de l'action ? Au-delà des contraintes d'équilibre, le vecteur gravitaire influence-t-il l'action de façon globale, jusqu'à la perception des mouvements de nos semblables ? Ces questions ont été celles qui ont guidé mes travaux de thèse. L'originalité de notre approche a été de placer l'exécution et la perception de l'action dans un « continuum fonctionnel » s'articulant autour des représentations internes de l'action. Pour ce faire, l'outil de choix qui est commun aux trois expériences de cette thèse est la microgravité (0G). Les expériences de cette thèse ont montré que les représentations internes de l'action se nourrissaient des informations graviceptives pour se construire et s'adapter constamment. Cependant, dans certaines conditions telle que la 0G à court terme, apparaît un ordre de priorité. En effet, le SNC est capable de mettre en place des solutions immédiates et efficaces pour l'exécution, comme en témoigne la repondération sensorielle rapide qui s'opère en 0G dans une tâche d'orientation posturale. Cependant, un temps de latence est observé dans la recalibration des modèles internes sur la base des afférences sensorielles fortement perturbées. C'est ce que nous avons montré grâce à un protocole d'imagerie motrice, mettant en évidence une perte de l'isochronie entre les mouvements exécutés et imaginés en 0G. Enfin, nous avons mis en évidence, chez des sujets sans expérience aucune de microgravité, que la perception du mouvement humain est efficace même lorsque ce dernier est exécuté en apesanteur, bien que des réseaux cérébraux différents soient mis en jeux. / What is the role of gravity in the internal representations of action? Beyond the constraints of balance, does the gravity vector influence the action globally, up to the perception of our peers' movement? These issues have guided my thesis work. The originality of our approach was to place the execution and the perception of action in a "functional continuum" built around the internal representations of the action. To do this, the tool of choice, that is common to all three experiments presented here, is microgravity (0G). The experiments of this thesis showed that the internal representations of action are fed with graviceptive information to build and adapt constantly. However, under certain conditions such as short-term 0G, an order of priority appears. Indeed, the CNS is able to implement immediate and effective solutions, as we demonstrate it with the fast sensorial reweighting observed during a postural orientation task. However, a lag is observed in the recalibration of internal models based on sensory inputs severely disrupted. This is what we have shown through a protocol of motor imagery, showing a loss of isochrony between executed and imagined movements under 0G. Finally, we have demonstrated in subjects without any experience of microgravity, that the perception of human movement is effective even when it is performed in weightlessness, although different cerebral networks are involved.

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Pas de résumé en français / Pas de résumé en anglais

Syftet med studien var att ta reda på vilka strategier elever väljer när de ska lösa ett matematiskt problem. Vi genomförde en observation och nio individuella intervjuer med elever i årskurs 3. De fick lösa ett matematiskt problem som observerades. Utifrån elevernas lösningar genomförde vi sedan intervjuer för att ta reda på vilka strategier de valt att använda för att lösa problemet. Resultatet av elevernas lösningar visade på flera olika lösningsstrategier. Dessa delades in i yttre och inre representationer. Strategier som bilder, grafiska framställningar och matematiska symboler (siffror) hör till de yttre representationerna, då de består av konkreta bilder som eleverna måste se framför sig på papper när de löser matematiska problem. Huvudräkning, automatiserad kunskap och ”tänkande” är samtliga strategier som tillhör de inre representationsformerna. Med inre representationer menar vi det som sker i huvudet, det eleverna inte behöver se framför sig för att kunna lösa problemet. Vi fann att elevlösningarna innehöll kombinationer av flera olika strategier. Vilken eller vilka strategier eleven än väljer till sin problemlösning är det oundvikligt att använda sig av någon form av inre representationsform, för att tänka måste alla göra oberoende av vilken lösningsstrategi som väljs och hur duktiga problemlösare eleverna än är. När eleverna är unga kan det vara svårt och ovant för dem att skriftligt redovisa hur lösningsprocessen gått till. Därför måste vi lärare ha tid att sätta oss in i hur eleven tänker för att kunna bygga vidare undervisningen utifrån den enskilde individens behov. / The purpose of the study was to discern which strategies pupils employ when they solve a mathematical problem. We carried through one observation and nine individual interviews with pupils in school year 3. They were asked to solve a mathematical problem, which was observed. On the basis of the pupils’ solutions, we carried out interviews in order to determine which strategies they chose to employ. The outcome of the pupils’ solutions showed several problem solving strategies. These were divided into external and internal representations. Strategies such as pictures, graphs and mathematical symbols (numerals) are external representations, as they consist of concrete pictures that the pupils must see in front of them on a paper when solving mathematical problems. Mental arithmetic, automated knowledge and “thinking” are all strategies that belong to internal modes of representation. With internal representations, we mean what happens inside our heads – what pupils need not see in front of them in order to solve a problem. We found that the pupils’ solutions contained combinations of several different strategies. Irrespective of which strategy or strategies the pupil choose in his or her problem solving, it is inevitable to use some variety of internal representations; everyone has to think, regardless of the strategy chosen and the problem solving skills of the pupil. When pupils are young, it may be difficult for them to present the flow of their problem solving processes in writing. Consequently, as teachers we must have time to familiarize ourselves with how the pupil thinks in order to develop our teaching on the basis of the needs of the individual pupil.

<p>Syftet med studien var att ta reda på vilka strategier elever väljer när de ska lösa</p><p>ett matematiskt problem. Vi genomförde en observation och nio individuella</p><p>intervjuer med elever i årskurs 3. De fick lösa ett matematiskt problem som</p><p>observerades. Utifrån elevernas lösningar genomförde vi sedan intervjuer för att</p><p>ta reda på vilka strategier de valt att använda för att lösa problemet. Resultatet av</p><p>elevernas lösningar visade på flera olika lösningsstrategier. Dessa delades in i</p><p>yttre och inre representationer. Strategier som bilder, grafiska framställningar och</p><p>matematiska symboler (siffror) hör till de yttre representationerna, då de består av</p><p>konkreta bilder som eleverna måste se framför sig på papper när de löser</p><p>matematiska problem. Huvudräkning, automatiserad kunskap och ”tänkande” är</p><p>samtliga strategier som tillhör de inre representationsformerna. Med inre</p><p>representationer menar vi det som sker i huvudet, det eleverna inte behöver se</p><p>framför sig för att kunna lösa problemet. Vi fann att elevlösningarna innehöll</p><p>kombinationer av flera olika strategier. Vilken eller vilka strategier eleven än</p><p>väljer till sin problemlösning är det oundvikligt att använda sig av någon form av</p><p>inre representationsform, för att tänka måste alla göra oberoende av vilken</p><p>lösningsstrategi som väljs och hur duktiga problemlösare eleverna än är. När</p><p>eleverna är unga kan det vara svårt och ovant för dem att skriftligt redovisa hur</p><p>lösningsprocessen gått till. Därför måste vi lärare ha tid att sätta oss in i hur</p><p>eleven tänker för att kunna bygga vidare undervisningen utifrån den enskilde</p><p>individens behov.</p> / <p>The purpose of the study was to discern which strategies pupils employ when they solve</p><p>a mathematical problem. We carried through one observation and nine individual</p><p>interviews with pupils in school year 3. They were asked to solve a mathematical</p><p>problem, which was observed. On the basis of the pupils’ solutions, we carried out</p><p>interviews in order to determine which strategies they chose to employ. The outcome of</p><p>the pupils’ solutions showed several problem solving strategies. These were divided</p><p>into external and internal representations. Strategies such as pictures, graphs and</p><p>mathematical symbols (numerals) are external representations, as they consist of</p><p>concrete pictures that the pupils must see in front of them on a paper when solving</p><p>mathematical problems. Mental arithmetic, automated knowledge and “thinking” are all</p><p>strategies that belong to internal modes of representation. With internal representations,</p><p>we mean what happens inside our heads – what pupils need not see in front of them in</p><p>order to solve a problem. We found that the pupils’ solutions contained combinations of</p><p>several different strategies. Irrespective of which strategy or strategies the pupil choose</p><p>in his or her problem solving, it is inevitable to use some variety of internal</p><p>representations; everyone has to think, regardless of the strategy chosen and the</p><p>problem solving skills of the pupil. When pupils are young, it may be difficult for them</p><p>to present the flow of their problem solving processes in writing. Consequently, as</p><p>teachers we must have time to familiarize ourselves with how the pupil thinks in order</p><p>to develop our teaching on the basis of the needs of the individual pupil.</p>