Similar to the development of speech in human infants, song learning in juvenile songbirds starts with memorization of adult vocalizations. Young birds develop their own song as a replica of a memorized adult song model through trial and error learning through abundant vocal practice. The internal model of this adult song, termed the ‘template’ is therefore central for guiding the process of vocal learning. However, even the most fundamental aspects of the template, such as when, where and how it is encoded in the brain, remain poorly understood. This dissertation attempts to define a paradigm where the onset of vocal learning and template formation can be time-locked to a small window of exposure to the tutor song. Using this paradigm, I further characterize the molecular changes accompanying the initial phase of vocal learning. The work described here shows that, in the zebra finch, template encoding can be time locked to, on average, a two-hour period of juvenile life and based on just 75 seconds of cumulative tutor song exposure. Rapid changes in vocal output induced by this exposure can be used as markers for predicting the future success of song imitation. To investigate the brain regions involved in this initial phase of vocal learning, a new approach was developed to interrogate global patterns of activity induced gene expression. Statistical parametric mapping, a method used for analysis of functional activity, was adapted to analyze regional activation across 3D reconstructions of whole brain gene expression maps. Using this approach, regions engaged at different stages of vocal learning were identified. To track the molecular mechanisms underlying these activation patterns, changes in the transcriptome of specific brain nuclei were analyzed as the young males undergo rapid changes in the vocal output in response to training. Significant changes in gene expression patterns were detected with divergent gene expression patterns across individual brain regions. The behavioral and molecular tools developed here present an important advance for understanding how the template is instantiated in the songbird brain.

In order to grasp an object in their visual field, humans orient their visual axis to targets of interest. While scanning their environment, humans perform multiple saccades (rapid eye movements that correct for a position error between eye and target) to align their visual axis with objects of interest. Humans are also able to track objects that move in their environment by means of smooth pursuit eye movements (slow eye movements that correct for any velocity error between eye and target, i.e. for any retinal slip). The appearance of a moving stimulus in the environment elicits smooth pursuit eye movements with a latency of around 100ms. Accordingly, the smooth pursuit system accounts for a change in the trajectory of a moving target with a similar delay. Due to this delay, the oculomotor system needs to develop strategies to avoid the build up of position error during tracking of a moving target. To do so, the oculomotor system uses prediction to try and anticipate the future target trajectory. However, this strategy is limited to conditions where target trajectory is predictable. Otherwise, primates have to combine pursuit and saccades in visual tracking of unpredictable moving targets to avoid large position error. This thesis focuses on both the prediction mechanisms and the interactions between saccades and pursuit. In order to investigate prediction mechanisms, we asked human subjects to pursue a moving target when it was transiently occluded. During occlusions, subjects continued to pursue the invisible target. This thesis demonstrates that this predictive pursuit response is based on a dynamic internal representation of target motion, i.e. a representation that evolves with time. This internal representation could be either built up by repetition of the same target motion or extrapolated on the basis of the pre-occlusion target motion. In addition, it is shown that during occlusions, saccades are adjusted in order to account for the large variability of the smooth pursuit response. As a consequence, it shows that the smooth pursuit command is used by internal models in order to predict future smooth pursuit response. These results demonstrate that both prediction and internal models are necessary to track the invisible and the visible.

The objects with which the hand interacts with may significantly change the dynamics of the arm. How does the brain adapt control of arm movements to this new dynamic? We show that adaptation is via composition of a model of the task's dynamics. By exploring generalization capabilities of this adaptation we infer some of the properties of the computational elements with which the brain formed this model: the elements have broad receptive fields and encode the learned dynamics as a map structured in an intrinsic coordinate system closely related to the geometry of the skeletomusculature. The low--level nature of these elements suggests that they may represent asset of primitives with which a movement is represented in the CNS.

No description available.

Internal models are believed to be crucial components in human motor control. It has been suggested that the central nervous system (CNS) uses forward and inverse models as internal representations of the motor systems. However, it is still unclear how the CNS implements the high-dimensional control of our movements. In this project, generative adversarial networks (GAN) are studied as a generative model of movement data. It is shown that, for a relatively small number of effectors, it is possible to train a GAN which produces new movement samples that are plausible given a simulator environment. It is believed that these models can be extended to generate high-dimensional movement data. Furthermore, this project investigates the possibility to use a trained GAN as an integrated forward and inverse model for motor control. / Interna modeller tros vara en viktig del av mänsklig rörelsekontroll. Det har föreslagits att det centrala nervsystemet (CNS) använder sig av framåtriktade modeller och inversa modeller för intern representation av motorsystemen. Dock är det fortfarande okänt hur det centrala nervsystemet implementerar denna högdimensionella kontroll. Detta examensarbete undersöker användningen av generativa konkurrerande nätverk som generativ modell av rörelsedata. Experiment visar att dessa nätverk kan tränas till att generera ny rörelsedata av en tvådelad arm och att den genererade datan efterliknar träningsdatan. Vi tror att nätverken även kan modellera mer högdimensionell rörelsedata. I projektet undersöks även användningen av dessa nätverk som en integrerad framåtriktad och invers modell.

This dissertation explores how children with and without developmental coordination disorder (DCD) ‘look’ and ‘see’: how they integrate vision and attention to guide arm and hand movements during a visuomotor task. Chapter 1 provides the thesis context, reviewing the vision and attention literature, outlining the role of these processes in motor performance, and reviewing what is known about vision and attention in children with DCD. Chapter 1 includes a discussion on eye tracking to measure visual attention, and outlines the thesis purpose and objectives.Chapter 2 focuses on children with DCD, detailing their presentation and clinical management. This chapter serves to increase the reader’s understanding of the difficulties children with DCD experience, and to demonstrate the need for intervention to prevent the profound consequences that can impact their quality of life. Chapter 3 presents a study that explores how children with and without DCD employ vision and attention to accomplish a visuomotor task in a natural setting, using a novel eye tracking design. Highlighted here are important differences during visuomotor task performance: compared to their peers, children with DCD did not use predictive gaze to attend to relevant task objects, but rather used vision to guide their arm/hand throughout the task. Chapter 4 outlines lessons learned from using an eye tracker with children with DCD, describing the children for whom eye tracking was not reliable, and discussing equipment and participant factors that impact eye tracker use. Recommendations for future research using eye tracking with the DCD population are provided. Finally, Chapter 5 discusses the clinical and research implications of the studies conducted here. Insights gained regarding visual attention differences between children with and without DCD are discussed in the context of interventions to improve health outcomes in children with DCD and the design of future eye tracking studies. / Dissertation / Doctor of Philosophy (PhD)

Ex-post intraday market-risk extrema are compared with ex-ante standard RiskMetrics parametric Value-at-Risk (VaR) limits for three foreign currency futures markets (British Pound, Japanese Yen, Swiss Frank) to determine whether forecasted volatility of market returns based on settlement price data provides a valid proxy for short-term market risk independent of market leverage. Intraday violations of ex-ante one-day VaR limits at the 95% confidence level should occur for less than 5% of market days. Violation frequencies for each of the markets tested are shown to occur well in excess of this 5% tolerance level: 9.54% for the British Pound, 7.09% for the Japanese Yen, and 7.79% for the Swiss Franc futures markets. Thus, it is empirically demonstrated that VaR is a poor proxy for short-term market risk under conditions of market leverage. Implications for managing (measuring, monitoring, controlling), reporting, and regulating financial market risk are discussed. / Master of Arts

Internal Models (IMs) play a significant role in autonomous robotics. They are mechanisms able to represent the input-output characteristics of the sensorimotor loop. In developmental robotics, open-ended learning of skills and knowledge serves the purpose of reaction to unexpected inputs, to explore the environment and to acquire new behaviours. The development of the robot includes self-exploration of the state-action space and learning of the environmental dynamics. In this dissertation, we explore the properties and benefits of the self-organisation of robot behaviour based on the homeokinetic learning paradigm. A homeokinetic robot explores the environment in a coherent way without prior knowledge of its configuration or the environment itself. First, we propose a novel approach to self-organisation of behaviour by artificial curiosity in the sensorimotor loop. Second, we study how different forward models settings alter the behaviour of both exploratory and goal-oriented robots. Diverse complexity, size and learning rules are compared to assess the importance in the robot’s exploratory behaviour. We define the self-organised behaviour performance in terms of simultaneous environment coverage and best prediction of future sensori inputs. Among the findings, we have encountered that models with a fast response and a minimisation of the prediction error by local gradients achieve the best performance. Third, we study how self-organisation of behaviour can be exploited to learn IMs for goal-oriented tasks. An IM acquires coherent self-organised behaviours that are then used to achieve high-level goals by reinforcement learning (RL). Our results demonstrate that learning of an inverse model in this context yields faster reward maximisation and a higher final reward. We show that an initial exploration of the environment in a goal-less yet coherent way improves learning. In the same context, we analyse the self-organisation of central pattern generators (CPG) by reward maximisation. Our results show that CPGs can learn favourable reward behaviour on high-dimensional robots using the self-organised interaction between degrees of freedom. Finally, we examine an on-line dual control architecture where we combine an Actor-Critic RL and the homeokinetic controller. With this configuration, the probing signal is generated by the exertion of the embodied robot experience with the environment. This set-up solves the problem of designing task-dependant probing signals by the emergence of intrinsically motivated comprehensible behaviour. Faster improvement of the reward signal compared to classic RL is achievable with this configuration.

Si la perception de notre environnement paraît simple et naturelle, les attributs visuels composant les différents objets sont traités dans des espaces temps qui leur sont propres en engageant des voies neuronales distinctes. La question du liage des informations sensorielles en un percept unique est alors posée. Dans le cadre de cette thèse, la question du liage sensoriel a été étudiée au regard des actes moteurs volontaires. En situation d'observation passive, le point de simultanéité subjective (PSS) montre qu'un changement de couleur doit se produire 40 ms avant un changement de position pour donner lieu à une perception synchrone des deux événements. L'exécution d'un mouvement d'atteinte manuelle réduit significativement ce PSS (-3.3 ms) uniquement lorsque le délai et l'écart spatial entre la fin de l'action motrice et les changements environnementaux n'excède pas 250 ms (-0,6 ms) et 2 cm ( 3,8 ms). Cependant, dans le cas où une situation d'apprentissage est induite par la présence de nouvelles contingences sensori-motrices, le liage sensoriel par l'action peut être observé pour des intervalles de temps plus grands (jusqu'à 1000 ms). Ce liage sensoriel par l'action, mis en évidence pour la première fois, serait sous-tendu par les mécanismes prédictifs associés aux modèles internes. Une dernière étude a révélé l'intérêt diagnostique de l'étude des relations perception/action au cours du vieillissement. Des profils de réponse spécifique ont été observés chez des patients de type Alzheimer lors de tâches testant les relations perception/action. Ces études apportent des arguments en faveur d'un rôle important de l'action dans la perception et la cognition. / If the perception of our environment seems easy and natural, the visual attributes of various objects are processed in space-time which are their own by engaging distinct neural pathways. The issue of binding of sensory information into a single percept is then arise. In this thesis, the issus of sensory bending was studied in relation to voluntary motor action. In position of passive observation, the point of subjective simultaneity (PSS) shows that a color change had to occur 40 ms before a change of position to give rise to a perception of two synchronous events. Performing a manual reaching movement reduced significantly the pSS (-3.3 ms) only when the time and space gap between the end of the motor action and environmental change does not exceed 250 ms (-0.6 ms) and 2 cm (3.8 ms). However, if a learning situation is induced by the presence of new sensorimotor contingencies, sensory binding by action can be observed for larger time intervals (up to 1000ms). This sensory binding by action, demonstrated for the first time, would be underpinned by predictive mechanisms associated with internal models. A last study showed the diagnostic interest of the study of relation perception/action during aging. Specific profiles of responses were observed in patients with Alzheimer on task testing the relations perception/action. These studies provide arguments for an important role of action in perception and cognition.

La gravité est omniprésente et affecte la dynamique de tous les mouvements que nous réalisons au quotidien. Variant de moins de 1% sur la surface terrestre, la force d’attraction gravitationnelle (9.81 m/s2) est actrice de l’évolution de toute espèce vivante. Grâce à un système sensoriel performant, les conséquences des effets de la gravité sur nos mouvements sont mémorisées sous la forme de représentations internes. Pour éviter d’être tributaires des délais temporels contraignants des signaux afférents du système sensoriel (trop longs si le mouvement doit être réalisé en urgence), l’individu agit de façon proactive en utilisant des modèles internes adaptés qu’il a notamment élaborés au cours de son expérience passée. Ces modèles sont utilisés essentiellement au cours d’une phase de planification motrice durant laquelle une commande motrice est définie pour initier l’action. La connaissance antérieure de notre système biomécanique et de notre environnement détermine donc l’ensemble des modèles internes de chaque individu. Cependant, à l’état initial, les retours sensoriels peuvent aussi être utilisés pour élaborer une stratégie motrice optimale. Pour anticiper au mieux les effets de la gravité, le rôle de ces informations initiales issues de feedback sensoriel reste encore à approfondir. C’est au cours de ces travaux de thèse que nous avons mis en évidence l’importance de ces informations avant l’exécution du mouvement. Une fois disponible (~100ms après le début du mouvement), les retours sensoriels disponibles sont alors intégrés aux modèles internes pour permettre un monitoring de la tâche motrice et éventuellement ajuster la stratégie au cours du mouvement. Ils sont d’autant plus utiles lorsque l’individu fait face à un nouveau contexte dynamique. En effet, l’individu va se fier davantage aux informations issues du système sensorimoteur, étant donné qu’il ne dispose d’aucun modèle interne adapté. C’est au cours d’une phase d’apprentissage que de nouveaux modèles internes vont être établis. Les facteurs qui permettent un apprentissage sont multivariés et dépendent du système sensoriel de chaque individu. Nous avons montré que lorsque tous les systèmes sensoriels subissent les effets d’un nouvel environnement gravito-inertiel, l’apprentissage était facilité. Ce résultat contraste avec le manque d’adaptation – voire les interférences – parfois observés lors d’apprentissages de tâches beaucoup plus simples. Tous ces mécanismes observables au niveau comportemental sont traités dans le cortex cérébral, et la prise en compte puis l’encodage des effets de la gravité sont effectués dans des aires cérébrales spécifiques. Si elles forment le réseau visuel vestibulaire lorsqu’il s’agit de prédire les effets de la gravité appliqués à des objets extérieurs, nous avons voulu savoir si le même réseau fonctionnel était responsable du traitement de la gravité lorsqu’il s’agissait de la production d’un mouvement. Nous avons mis en évidence que le cortex insulaire est le siège de ce réseau vestibulaire. Ainsi, grâce à une étude d’imagerie mentale qui n’induit pas de mouvement, nous avons également pu observer des différences de circuiterie au sein même de l’insula lorsque des informations gravitaires utiles fournies par les capteurs sensoriels, en particulier proprioceptifs, sont transmises (phase d’exécution), ou non (phase de planification du mouvement) au cerveau. / Gravity is immutable, ubiquitous and affects the dynamic of our daily movements. The gravitational attraction (9.81 m / s2) which varies less than 1% of the earth's surface, is an actress of the evolution of all living species. Thanks to an efficient sensorimotor system, the dynamical consequences of the effects of gravity on our movements are stored as internal representations. To circumvent the time delays of the afferent signals coming from the sensorimotor system (too long to plan quick movements), the Central Nervous System (CNS) acts in a proactive fashion by using suitable internal models developed during our past experiences. These models are mainly used during the motor planning to provide a motor command to initiate the action. Prior knowledge of our biomechanical system and our environment therefore characterizes the diversity of internal models of each individual. However, before movement’s execution, sensory feedback can also be used to develop an optimal strategy of the motor task. The role of this initial information coming from the sensory feedback to anticipate the effects of gravity remains to deepen. During this thesis, we have highlighted the critical role of the initial information to plan a movement. Once available (~ 100 ms after the beginning of the movement), the sensory feedback is then integrated into internal models to control the motor task and if it is necessary, to adjust the strategy during movement execution. The initial information is especially useful when we have to deal with a new dynamical context. Indeed, the CNS will much more rely on this information coming from the sensorimotor system, given that no internal model related to the unusual context has still been developed. During a learning phase new internal models will be established. The parameters which allow learning are various and depend on the sensorimotor system of each individual. We have shown that when all the sensory systems are affected by the effects of a new gravito-inertial environment, learning was facilitated. This result contrasts with the lack of adaptation - or interference - sometimes observed during learning tasks much easier. All these mechanisms observed at a behavioral stage are processed in the cerebral cortex, and the integration and encoding of the effects of gravity are processed in specific brain areas. In particular, concerning external objects, the vestibular network is engaged to predict the effects of gravity. Thus, we wanted to know if the same functional network was responsible of the processing of the dynamical constraints of gravity during movement’s execution. We have shown that the insular cortex, which is the core region of the visual vestibular system, plays an important role. Then, by using mental imagery paradigm that does not induce movement, we also observed differences in the circuitry within the insula when gravity-relevant signals related to movement’s execution are transmitted or not to the brain.