Neurally Plausible Model of Robot Reaching Inspired by Infant Motor Babbling

In this dissertation, we present an abstract model of infant reaching that is neurally-plausible. This model is grounded in embodied artificial intelligence, which emphasizes the importance of the sensorimotor interaction of an agent and the world. It includes both learning sensorimotor correlations through motor babbling and also arm motion planning using spreading activation. We introduce a mechanism called bundle formation as a way to generalize motions during the motor babbling stage. We then offer a neural model for the abstract model, which is composed of three layers of neural maps with parallel structures representing the same sensorimotor space. The motor babbling period shapes the structure of the three neural maps as well as the connections within and between them; these connections encode trajectory bundles in the neural maps. We then investigate an implementation of the neural model using a reaching task on a humanoid robot. Through a set of experiments, we were able to find the best way to implement different components of this model such as motor babbling, neural representation of sensorimotor space, dimension reduction, path planning, and path execution. After the proper implementation had been found, we conducted another set of experiments to analyze the model and evaluate the planned motions. We evaluated unseen reaching motions using jerk, end effector error, and overshooting. In these experiments, we studied the effect of different dimensionalities of the reduced sensorimotor space, different bundle widths, and different bundle structures on the quality of arm motions. We hypothesized a larger bundle width would allow the model to generalize better. The results confirmed that the larger bundles lead to a smaller error of end-effector position for testing targets. An experiment with the resolution of neural maps showed that a neural map with a coarse resolution produces less smooth motions compared to a neural map with a fine resolution. We also compared the unseen reaching motions under different dimensionalities of the reduced sensorimotor space. The results showed that a smaller dimension leads to less smooth and accurate movements

Learning to grasp and extract affordances: the Integrated Learning of Grasps and Affordances (ILGA) model

The activity of certain parietal neurons has been interpreted as encoding affordances (directly perceivable opportunities) for grasping. Separate computational models have been developed for infant grasp learning and affordance learning, but no single model has yet combined these processes in a neurobiologically plausible way. We present the Integrated Learning of Grasps and Affordances (ILGA) model that simultaneously learns grasp affordances from visual object features and motor parameters for planning grasps using trial-and-error reinforcement learning. As in the Infant Learning to Grasp Model, we model a stage of infant development prior to the onset of sophisticated visual processing of hand–object relations, but we assume that certain premotor neurons activate neural populations in primary motor cortex that synergistically control different combinations of fingers. The ILGA model is able to extract affordance representations from visual object features, learn motor parameters for generating stable grasps, and generalize its learned representations to novel objects

The effectiveness of PROMPT therapy for children with cerebral palsy

The purpose of this study is to evaluate the effectiveness of a motor speech treatment approach (PROMPT) in the management of motor-speech impairment in children with cerebral palsy. Two main objectives were addressed: (1) to evaluate changes in speech intelligibility and, (2) evaluate changes in kinematic movements of the jaw and lips using three dimensional (3D) motion analysis.A single subject multiple-baseline-across-participants research design, with four phases: Baseline (A1), two intervention phases (B and C) and maintenance (A2), was implemented.Six participants, aged 3-to-11-years (3 boys, 3 girls) with moderate to severe speech impairment were recruited through The Centre for Cerebral Palsy, Western Australia (TCCP). Inclusion criteria were: diagnosis of cerebral palsy, age 3 – 14 years, stable head control (supported or independent), spontaneous use of at least 15 words, speech impairment ≥1.5 standard deviations, hearing loss no greater than 25dB, developmental quotient ≥70 (Leiter-Brief International Performance Scale R) and no previous exposure to PROMPT. Thirteen typically-developing peers were recruited to compare the trend of kinematic changes in jaw and lip movements to those of the children with cerebral palsy.Upon achievement of a stable baseline, participants completed two intervention phases both of 10 weeks duration. Therapist fidelity to the PROMPT approach was determined by a blinded, independent PROMPT Instructor.Perceptual outcome measures included the administration of weekly speech probes, containing trained and untrained vocabulary at the two targeted levels of intervention plus an additional level. These were analysed for both perceptual accuracy (PA) and the motor speech movement parameter. End of phase measures included: 1. Changes in phonetic accuracy as measured using a measure of percentage phonemes correct; 2. Speech intelligibility measures, using a standardised assessment tool; and 3. Changes to activity/participation using the Canadian Occupational Performance Measure (COPM).Kinematic data were collected at the end of each study phase using 3D motion analysis (Vicon Motus 9.1). This involved the collection of jaw and lip measurements of distance, duration and velocity, during the production of 11 untrained stimulus words. The words contained vowels that spanned the articulatory space and represented motor-speech movement patterns at the level of mandibular and labial-facial control, as classified according to the PROMPT motor speech hierarchy.Analysis of the speech probe data showed all participants recorded a statistically significant improvement. Between phases A1-B and B-C 6/6 and 4/6 participants respectively, recorded a statistically significant increase in performance level on the motor speech movement patterns (MSMPs) targeted during the training of that intervention priority (IP). The data further show that five participants (one participant was lost to follow-up) achieved a statistically significant increase at 12- weeks post-intervention as compared to baseline (phase A1).Four participants achieved a statistically significant increase in performance level in the PA of the speech probes of both IP1 and IP2 between phases A1-B. Whilst only one participant recorded a statistically significant increase in PA between phases BC, five participants achieved a statistically significant increase in IP2 between phases A1-C. The data further show all participants achieved a statistically significant increase in PA on both intervention priorities at 12-weeks post-intervention. All participants recorded data that indicated improved perceptual accuracy across the study phases. This was indicated by a statistically significant increase in the percentage phonemes correct scores F(3,18) = 5.55, p<.05.All participants achieved improved speech intelligibility. Five participants recorded an increase in speech intelligibility greater than 14% at the end of the first intervention (phase B). Continued improvement was observed for 5 participants at the end of the second intervention (phase C)

Haptic foundations for visually guided action

Prehension is proposed to consist of two movements mediated by separate neural pathways – a Reach transports the hand to the target while a Grasp shapes the hand for target purchase – but under vision the two movements appear as a seemless act. The purpose of the present thesis was to examine prehension under conditions of limited visual feedback. Removing vision in adults caused prehension to decompose into an open handed Reach followed by a haptically mediated Grasp, suggesting that haptics also access the Reach and Grasp pathways. That Grasp, but not Reach, formation is equally accurate under haptic versus visual control indicates that the sensory control of the two movements can be differentiated. Finally, young infants perform haptic Reach and Grasp movements before integrating them together under vision. These results suggest that the Reach and the Grasp, with their requisite neural pathways, originate under haptic control with secondary access by vision.AIHS, NSER

Unsupervised learning of vocal tract sensory-motor synergies

The degrees of freedom problem is ubiquitous within motor control arising out of the redundancy inherent in motor systems and raises the question of how control actions are determined when there exist infinitely many ways to perform a task. Speech production is a complex motor control task and suffers from this problem, but it has not drawn the research attention that reaching movements or walking gaits have. Motivated by the use of dimensionality reduction algorithms in learning muscle synergies and perceptual primitives that reflect the structure in biological systems, an approach to learning sensory-motor synergies via dynamic factor analysis for control of a simulated vocal tract is presented here. This framework is shown to mirror the articulatory phonology model of speech production and evidence is provided that articulatory gestures arise from learning an optimal encoding of vocal tract dynamics. Broad phonetic categories are discovered within the low-dimensional factor space indicating that sensory-motor synergies will enable application of reinforcement learning to the problem of speech acquisition

Laterality and Babble: Does asymmetry in lip opening during babble indicate increasing left hemisphere dominance as babies gain articulatory experience?

Speech and language are supported by task-dependent neural networks that are predominantly lateralised to the left hemisphere of the brain, whilst emotion is supported by predominantly right hemispheric networks. This is reflected in the asymmetry of lip openings during speech and facial expressions in adults. One cross-sectional orofacial asymmetry study found an analogous distinction between 5-12-month-old babies’ lip openings during reduplicated babble and during positively valenced emotional facial expressions and this has been interpreted as evidence to support the hypothesis that babble is fundamentally linguistic in nature (Holowka & Petitto, 2002). However, a similar distinction is also observed in orofacial behaviours in some non-human primates. Differential hemispheric specialisation for emotional and vocal communicative functions may then be an ancient trait, long predating human language. Additionally, characterising babble as babies’ immature attempts to do language marginalises the critical role of endogenously motivated vocal exploration and may assume a degree of goal-directedness in infant behaviour around the time of babble emergence for which we have little other supporting evidence. This thesis explores laterality in eight 5-12-month-old’s babble, positive facial expressions, and other vocalisations longitudinally. Singleton and variegated babble are captured as well as reduplicated babble, and an alternative method for analysing orofacial asymmetry – hemimouth measurement – is used. Overall, Holowka and Petitto’s between-category distinction was replicated. However, babble was found to show right laterality at emergence and become left lateralised gradually over developmental time. Some interactional effect of utterance complexity was also observed. Bisyllabic babbles showed significant leftward shift over developmental time, whilst monosyllabic and polysyllabic babbles did not. Furthermore, hemimouth measurement revealed a degree of real-time variability in the laterality of babble not previously observed. An alternative theory of the underlying nature of babble – the Old Parts, New Machine hypothesis – is proposed

Sensorimotor planning, integration, and execution processes in autism spectrum disorders

The focus of this thematic thesis was to conduct an examination into the autistic differences to underlying sensorimotor planning, integration, and execution processes. The distinct protocols in the current programme of work: imitation in upper-limb motor control (chapter two), upper-limb single and two-segment manual aiming (chapter three) and stepping behaviour in obstacle crossing (chapter four), provide independent, yet related, examinations of underlying autistic sensorimotor behaviour compared to typically developing controls. Chapter two revealed that autistic participants successfully imitated atypical biological motion kinematics when the imitation environment was structured to facilitate trial-by-trial processing, and interference in the inter-trial delay over time influenced consolidatory offline sensorimotor processes related to planning. Chapter three revealed that autistic adolescents show significant alterations to sensorimotor planning processes during single and two-segment manual aiming. Chapter four revealed significant sensorimotor integration differences during obstacle crossing in autistic participants who require substantial or very substantial support. Across all experimental chapters in the current thesis, there also appeared to be significant autistic variability increases across several key dependant variables, implicating altered sensorimotor feedforward planning processes. Additionally, there also appears to be evidence of intact sensorimotor feedback processes whereby autistic participants utilise the online integration of sensory information to compensate for earlier variabilities. This thesis will seek to synthesise, summarise, and appraise key findings between experimental chapters, relative to current literature, with both theoretical and wider implications for the motor control and autistic communities discussed and future directions identified

EEG and TMS-EEG Studies on the Cortical Excitability and Plasticity associated with Human Motor Control and Learning

More than half of the activities of daily living rely on upper limb functions (Ingram et al., 2008). Humans perform upper limb movements with great ease and flexibility but even simple tasks require complex computations in the brain and can be affected following stroke leaving survivors with debilitating movement impairments. Hemispheric asymmetries related to motor dominance, imbalances between contralateral and ipsilateral primary motor cortices (M1) activity and the ability to adapt movements to novel environments play a key role in upper limb motor control and can affect recovery. Motor learning and control are critical in neurorehabilitation, however to effectively integrate these concepts into upper limb recovery treatments, a deeper understanding of the basic mechanisms of unimanual control is needed. This thesis aimed to investigate hemispheric asymmetries related to motor dominance, to evaluate the relative contribution of the contralateral and ipsilateral M1 during unilateral reaching preparation and finally to identify the neural correlates underlying the formation of a predictive internal model enabling to adapt movements to new environments. To this end electroencephalography (EEG), transcranial magnetic stimulation (TMS), simultaneous TMS-EEG were employed during a simple motor and a highly standardised robot-mediated task. The first study used TMS-EEG to examine differences in cortical excitability related to motor dominance by applying TMS over the dominant and non-dominant M1 at rest and during contraction. No hemispheric asymmetries related to hand dominance were found. The second study assessed the temporal dynamics of bi-hemispheric motor cortical excitability during right arm reaching preparation. TMS was applied either to the ipsilateral or contralateral M1 during different times of movement preparation. Significant bilateral M1 activation during unilateral reaching preparation was observed, with no significant differences between the contralateral and ipsilateral M1. Unimanual reaching preparation was associated with significant interactions of excitatory and inhibitory processes in both motor cortices. The third study investigated the neural correlates of motor adaptation. EEG was recorded during a robot-mediated adaptation task involving right arm reaching movements and cortical excitability was assessed by applying TMS over the contralateral M1 and simultaneously recording TMS responses with EEG before and after motor adaptation. It was found that an error-related negativity (ERN) over fronto-central regions correlated with performance improvements during adaptation, suggesting that this neural activity reflects the formation of a predictive internal model. Motor adaptation underlay significant modulations in cortical excitability (i.e. neuroplasticity) in sensorimotor regions. Finally, it was shown that native cortical excitability was linked to motor learning improvements during motor adaptation and explained the variability in motor learning across individuals. These experiments demonstrated that even unimanual motor control relies on interactions between excitatory and inhibitory mechanisms not only in the contralateral M1 but in a wider range of brain regions, shown by a bi-hemispheric activity during movement preparation, the formation of a predictive model in fronto-central regions during motor adaptation and neuroplastic changes in sensorimotor regions underlying motor adaptation during unimanual reaching

THE POTENTIATION OF ACTIONS BY VISUAL OBJECTS

This thesis examines the relation between visual objects and the actions they afford. It is proposed that viewing an object results in the potentiation of the actions that can be made towards it. The proposal is consistent with neurophysiological evidence that suggests that no clear divide exists between visual and motor representation in the dorsal visual pathway, a processing stream that neuropsychological evidence strongly implicates in the visual control of actions. The experimental work presented examines motor system involvement in visual representation when no intention to perform a particular action is present. It is argued that the representation of action-relevant visual object properties, such as size and orientation, has a motor component. Thus representing the location of a graspable object involves representations of the motor commands necessary to bring the hand to the object. The proposal was examined in a series of eight experiments that employed a Stimulus- Response Compatibility paradigm in which the relation between responses and stimulus properties was never made explicit. Subjects had to make choice reaction time responses that mimicked a component of an action that a viewed object afforded. The action-relevant stimulus property was always irrelevant to response determination and consisted of components of the reach and grasp movement. The results found are not consistent with explanations based on the abstract coding of stimulus-response properties and strongly implicate the involvement of the action system. They provide evidence that merely viewing an object results in the activation of the motor patterns necessary to interact with them. The actions an object affords are an intrinsic part of its visual representation, not merely on account of the association between objects and familiar actions but because the motor system is directly involved in the representation of visuo-spatial object properties

A Curious Robot Learner for Interactive Goal-Babbling (Strategically Choosing What, How, When and from Whom to Learn)

Les dé s pour voir des robots opérant dans l environnement de tous les jours des humains et sur unelongue durée soulignent l importance de leur adaptation aux changements qui peuvent être imprévisiblesau moment de leur construction. Ils doivent être capable de savoir quelles parties échantillonner, et quelstypes de compétences il a intérêt à acquérir. Une manière de collecter des données est de décider par soi-même où explorer. Une autre manière est de se référer à un mentor. Nous appelons ces deux manièresde collecter des données des modes d échantillonnage. Le premier mode d échantillonnage correspondà des algorithmes développés dans la littérature pour automatiquement pousser l agent vers des partiesintéressantes de l environnement ou vers des types de compétences utiles. De tels algorithmes sont appelésdes algorithmes de curiosité arti cielle ou motivation intrinsèque. Le deuxième mode correspond au guidagesocial ou l imitation, où un partenaire humain indique où explorer et où ne pas explorer.Nous avons construit une architecture algorithmique intrinsèquement motivée pour apprendre commentproduire par ses actions des e ets et conséquences variées. Il apprend de manière active et en ligne encollectant des données qu il choisit en utilisant plusieurs modes d échantillonnage. Au niveau du metaapprentissage, il apprend de manière active quelle stratégie d échantillonnage est plus e cace pour améliorersa compétence et généraliser à partir de son expérience à un grand éventail d e ets. Par apprentissage parinteraction, il acquiert de multiples compétences de manière structurée, en découvrant par lui-même lesséquences développementale.The challenges posed by robots operating in human environments on a daily basis and in the long-termpoint out the importance of adaptivity to changes which can be unforeseen at design time. The robot mustlearn continuously in an open-ended, non-stationary and high dimensional space. It must be able to knowwhich parts to sample and what kind of skills are interesting to learn. One way is to decide what to exploreby oneself. Another way is to refer to a mentor. We name these two ways of collecting data sampling modes.The rst sampling mode correspond to algorithms developed in the literature in order to autonomously drivethe robot in interesting parts of the environment or useful kinds of skills. Such algorithms are called arti cialcuriosity or intrinsic motivation algorithms. The second sampling mode correspond to social guidance orimitation where the teacher indicates where to explore as well as where not to explore. Starting fromthe study of the relationships between these two concurrent methods, we ended up building an algorithmicarchitecture with a hierarchical learning structure, called Socially Guided Intrinsic Motivation (SGIM).We have built an intrinsically motivated active learner which learns how its actions can produce variedconsequences or outcomes. It actively learns online by sampling data which it chooses by using severalsampling modes. On the meta-level, it actively learns which data collection strategy is most e cient forimproving its competence and generalising from its experience to a wide variety of outcomes. The interactivelearner thus learns multiple tasks in a structured manner, discovering by itself developmental sequences.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF