This dissertation aims to understand how attention can be used to improve sensory integration for postural control. Decades of research have been done using visual manipulations to study how healthy and clinical populations resolve multisensory (vision, vestibular, and somatosensory) mismatches to maintain postural stability. Postural control is a complex motor skill that requires accurate integration of multiple senses to maintain body alignment and orientation with respect to the environment. Age-related decline in visual, vestibular, and somatosensory acuity increases the risk for falls, and these sensory declines can be identified by assessing sensory reweighting. Sensory reweighting is the process in which the nervous redistributes the reliance, or "weight," on the sensory inputs to achieve postural stability. While the literature on sensory manipulation on postural control and fall risk has uncovered a wealth of knowledge on sensory reweighting for balance, it has neglected to identify how sensory reweighting can be improved. At the same time, motor learning literature has demonstrated the importance of focus attention during balance training to improve postural control. However, rudimentary analyses such as duration of balance and sway variability in this literature have limited deeper examination of the underlying neural mechanisms affected by focus of attention. This dissertation aims to bridge the gap between the two works of literature by implementing sensory manipulation techniques on posture using the latest technologies in virtual reality (VR) head-mount display (HMD) with motion capture and electroencephalography (EEG) recordings to study how different focuses of attention help resolve multisensory conflicts. In aim one, forty-two healthy adults participated in the study that used VR manipulation to induce a multisensory conflict. Participants were tasked to maintain upright stability on a rocker board while given different instructions on where to focus their attention. Instructions included focusing on keeping the rocker board leveled (external focus), focusing on keeping feet leveled to each other (internal focus), and focusing on staying as still as possible (control). This study revealed an immediate improvement in postural stability when instructed with external focus compared to control. This improvement was also associated with a significant decrease in visual weighting. Additionally, this aim revealed an immediate change in cortical activity within the frontal and occipital regions of the brain as identified by EEG recordings when participants are instructed to use external focus and internal focus. In aim two, twenty-eight healthy adults participated in the crossover study that demonstrated order effects when multiple instructions of attentional focus were given to the same participant for postural stability and visual reweighting. This study showed that the effects of external focus on postural stability and visual reweighting are greater when external focus is used before internal focus. However, the effects of external focus were nullified when used after using internal focus. Furthermore, the order of the instructions may have corresponded with a recency bias regarding how the participant perceived the effectiveness depending on when they received the attentional focus instruction. Guided by the findings from aims one and two, aim three recruited twenty-seven older adults to participate in a single-session balance training using repeated exposure to VR manipulation that challenged their balance on a rocker board. The older adults were randomized into one of the three groups: external focus, internal focus, and control group. The external focus group did not demonstrate an immediate reduction in visual weighting as found in aim 1. However, the external focus group did demonstrate better immediate postural stability when compared to the internal focus groups. Both external and internal focus groups revealed a significant improvement in visual weighting and postural stability across training blocks, suggesting a potential role of attentional focus on postural control adaption to repeated VR exposure. This dissertation was one of the first studies to investigate how the attentional focus impacts sensory reweighting and postural control in young and older adults using VR HMD. This project also established a VR experimental paradigm that can be used to study the focus of attention and the resolution of multisensory mismatch. With the increased use of VR for balance training and rehabilitation, this project is at the forefront of utilizing VR HMD technology to expose underlying sensory mechanisms for postural control. Results from this study can guide future rehabilitation and balance training interventions by identifying how attention should be directed during training. / Public Health

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When examining objects using tactile senses, individuals often incorporate multiple sources of haptic sensory information to estimate the object’s properties. How do our brains integrate various cues to form a single percept of the object? Previous research has indicated that integration from cues across sensory modalities is optimally achieved by weighting each cue according to its variance, such that more reliable cues have more weight in determining the percept. To explore this question in the context of a within-modality haptic setting, we assessed participants’ perception of edges that cross the index, middle, and ring fingers of the right hand. We used a 2-interval forced choice (2IFC) task to measure the acuity of each digit individually, as well as the acuity of all three digits working together, by asking participants to distinguish the locations of two closely spaced plastic edges. In examining the data, we considered three perceptual models, an optimal (Bayesian) model, an unweighted average model, and a winner-take-all model. The results indicate that participants perceived sub-optimally, such that the acuity of the three digits together did not exceed that of the best individual digit. We further investigated our question by having participants unknowingly undergo a 2IFC cue conflict condition, where they thought they were touching a straight edge which was actually staggered and thus gave each digit a different positional cue. Our analyses indicate that participants did not undertake optimal cue combination but are inconclusive with respect to which suboptimal strategy they employed. / Thesis / Master of Science (MSc) / This thesis investigates the neural mechanisms behind tactile perception, specifically how the brain combines multiple sensory cues to construct a unified percept when interacting with objects through touch. Typically, optimal sensory integration involves assigning more weight to more reliable cues. Our research focused on tactile integration by examining participants’ ability to perceive the positions of edges crossing their index, middle, and ring fingers simultaneously. The results indicated that, contrary to predictions, participants exhibited various sub-optimal cue integration strategies. Their ability to perceive the combined positions of all three fingers was not superior to that of the best-performing individual finger. We also explored cue conflict situations, where the locations of the tactile cues were no longer from a straight edge, unbeknown to participants, and the results here reinforced the finding that participants did not consistently employ optimal cue combination strategies. This research offers valuable insights into how the brain processes tactile information.

In recent years, computational neuroscientists have suggested that human behaviour, including perception, occurs in a manner consistent with Bayesian inference. According to the Bayesian ideal observer model, the observer combines cues from multiple sensory streams as a weighted average based on each cue’s reliability. Most cue-combination research has focused on integration of cues between sensory modalities or within the visual modality. Cue combination within the tactile modality has been relatively rarely studied, and it is still not known whether cues from individual digits combine optimally. In this thesis, we use the ideal observer model to determine whether cues from three different digits are combined optimally. We predicted that cues from multiple digits would be combined according to the optimal cue combination model. To test our hypothesis, we devised a two-interval forced choice (2IFC) task where participants had to discriminate the distal/proximal location of a 1-mm thick edge across the fingerpad(s) of the index (D2), middle (D3), and ring (D4) fingers. We used a Bayesian adaptive method, the ψ method, to compute participants’ psychometric functions for single-digit (D2, D3, and D4) and multiple-digit (D23, D24, D34, and D234) conditions. We determined the stimulus level ∆x, the distance (mm) between the distal and proximal stimuli locations, at 76% correct probability. This distance corresponds to a sensitivity index d'=1 and is the σ value of the participant’s stimulus measurement distribution. We then used the single-digit σ values to predict optimal cue combination for the multiple-digits combinations. We did not observer optimal cue-combination between the digits in this study. We outline potential implications the results of this experimental have on determining how the nervous system combines cues between digits, focusing on theoretical and experimental updates to the experiment that might result in the observation of optimal cue combination between digits. / Thesis / Master of Science (MSc)

The COVID-19 pandemic has significantly affected the mental health and well-being of young students, particularly those aged three to five, leading to disruptions in their daily routines and sensory dysregulation. The Sensory Diet Center (SDC) program offers a structured schedule of personalized sensory activities for early-grade students to regulate sensory input effectively within the classroom environment. By providing various sensory experiences, the Sensory Diet Center program aims to enhance students' sensory processing skills, attention, self-regulation, and readiness for academic tasks and social interactions. Utilizing evidence-based practices, the SDC program fosters a sensory-friendly classroom environment that promotes interactive play, social connections, and overall well-being. Offered twice daily for 30 minutes each, the SDC program targets tactile, proprioception, and vestibular systems, creating a balanced sensory environment that supports students' development of necessary academic and social skills. The author includes a funding plan that will assist in purchasing the necessary items to make the proposed intervention successful. In addition, this doctoral paper provides a comprehensive program evaluation plan highlighting the key stakeholders and a multiple baseline study designed to evaluate the program's effectiveness.

The thesis is foccused on the problematics of the developmental coordination disorder and its presence within the patiens with the idiopathic scoliosis. The theoretical part deals with the explanation of the terms of developmental coordination disorder, sensory integration and idiopathic scoliosis. The experimental part looks for the connection among the idiopathic scoliosis and the dvelopmental dyspraxia. Thirty patients took part in it. Eighteen of them were patiens with the idiopathic scoliosis, these were divided into two groups according to the age. The first group at the age of 7 to 10 years counted four patiens, the other group from 11 to 16 years contained fourteen patiens. The controll group involved twelve children from the fifth class of the common primary school. The children were tested by the standardized Movement Assessment Battery for Children 2 (MABC-2). Furthermore the measurement was completed by two questionnaires for parents. In the DCDQ'07 they assessed the motor abilities of their child compared to children of the same age and gender. The other questionnaire was aimed at closer information obout the pregnancy, development of the child, presence of any disease or impairment, etc. The difference between motor skills of children with the idiopathic scoliosis and the controll group in...

This written work is about the the peculiarity of sencomotorical education of the children, who’s age is from 5 to 7 with the severe complex disability. The children with the severe complex disability are known as the children with many intellectual, hearing, visual, body and position, speech and communication disorders. The level of psychomotorical growth doesn’t match their biological age. During the educational process of the children with severe complex disability, of the age from5 to 7 years old, many difficulties are coming up. They are: the difficulty to estimate the level of their perception, the difficulty to adapt the programs, the difficulty to fix the impact of the program on the child’s development. There is an opinion that it is possible to make an impact on the child’s development by stimulation of his basic sensations. This written work is a research on the impact of the sensomotorical educational program on the psychomotorical development of the children, who’s age is from 5 to 7 with the severe complex disability. The reactions on the sensomotorical stimulation and the changes in their abilities were observed and fixed. The theoretical part explains the development of the healthy child from birth and till the 9th month, it also gives the understanding of the developmental disorders and their groups, it shows the problems and the peculiarity of education of the children, who’s age is from 5 to 7 with the severe complex disability. The educational quantity... [to full text]

Un simulateur de conduite dynamique est un outil permettant, entre autres, d’étudier les processus d’intégration multi-sensorielle pour la perception du mouvement et la production du comportement de conduite. Néanmoins, les limitations mécaniques des simulateurs, qui imposent des stratégies dynamiques pour simuler le réel, peuvent avoir un impact défavorable sur la perception et le comportement du conducteur. Cette problématique est particulièrement vraie pour la prise de virages qui demeure une situation difficile à reproduire de façon réaliste notamment à cause des variations importantes d’accélérations latérales. Dans ce contexte, cette thèse présente des travaux de recherches permettant de mieux comprendre les processus d’intégration multi-sensorielle (rôle des informations inertielles et visuelles) pour la perception du mouvement en virages et de caractériser l’évolution d’un percept en fonction des conditions de simulation.En conclusion, il a été démontré que la perception des accélérations latérales est basée sur des processus non-linéaires. Le rôle des informations visuelles et inertielles semble donc dépendre des individus et du contexte (notamment du niveau des accélérations latérales) dans lequel ces stimulations sont produites. Sur la base de l’ensemble de ces résultats, des nouvelles pistes d’amélioration du simulateur dynamique SHERPA² de PSA sont proposées. Il est préconisé notamment d’employer un gain du mouvement latéral dégressif avec l’augmentation du niveau d’accélération latérale. / A dynamic driving simulator is a tool, among others, allowing the study of multisensory integration for motion perception and production of driving behavior. Nevertheless, the mechanical limitations of the simulators which impose dynamic strategies to simulate the real can have an adverse negative impact on the driver perception and its behavior. This issue is particularly true for cornering which remains a difficult situation to reproduce in a realistic way, because of massive lateral accelerations variations. In this context, this thesis presents research works allowing to understand the processes of multisensory integration (role of inertial and visual information) for the motion perception in cornering and to characterize the evolution of a percept as a function of simulation conditions.In conclusion, it has been demonstrated that the perception of lateral accelerations is based on non-linear processes. The roles of visual and inertial information seem to depend on the individuals and on the context (notably the level of lateral accelerations) in which these stimulations are produced. Base on of the overall results, new ways for improvement of the dynamic driving simulator SHERPA2 are proposed. It is notably preconized to employ a lateral motion gain digressive with the increase of lateral acceleration.

Abstract This essay examines which role functional oriented music therapy, which is supposed to help sensorimotor development, can have in schools and in health care. To find this out, research about what kinds of effects exercise can have on academic achievements and in recovery from brain injuries has been brought up. The research concerning academic achievements was conducted with school children; some children without difficulties, some with sensory integration problems, and some with motor skill difficulties. In addition to this, research about the brain structure superior colliculus, which lies behind sensory integration, is also brought up. The results showed that children who were given more exercise had significantly better scores in academic skills than the children with normal academic education. Thus, it might be reasonable to practise functional oriented music therapy in schools, both as helping general development, but also for children with different types of difficulties. The research concerning exercise and injuries has made clear that the adult brain can change via neurogenesis, plasticity and cortical reorganization. These three aspects are important when practicing a skill or when recovering from an injury. Exercise has been shown to affect these three aspects positively and can therefore also aid the recovery from injuries. Thus, there seems to be many theoretical aspects supporting the FMT- method. However, the question is if the results of one treatment form can generalize over such a wide range of injuries and defects that the FMT –adepts usually have. It is therefore also discussed if further experiments on the FMT-method could help make it a more effective tool for rehabilitation.

Le syndrome d’Ehlers-Danlos (SED) est un groupe mixte de maladies héréditaires dont la caractéristique commune est une altération d’origine génétique du tissu conjonctif. Sa forme hypermobile (SEDh) se caractérise par une hypermobilité articulaire généralisée, associée à une hyperélasticité cutanée, générant toutes deux un déficit somesthésique. Or, le système somesthésique est, avec les systèmes visuel et vestibulaire, crucialement impliqué dans le fonctionnement du système sensorimoteur. Ce travail de thèse visait donc à comprendre comment le déficit somesthésique propre au SEDh modifie les mécanismes perceptifs et sensorimoteurs sous-tendant le contrôle postural. L’appréhension de ces mécanismes s’est articulée autour de deux types d’approches : l’une indirecte, au travers de l’étude des mécanismes sensoriels sous-tendant la perception de la verticale, et l’autre directe, au travers d’analyses posturographiques approfondies.Le premier objectif de travail visait à déterminer comment le déficit somesthésique affecte l’utilisation des cadres de référence spatiale (allocentré, égocentré et géocentré) pour la perception de la verticale visuelle. Pour ce faire, nous avons conduit deux études évaluant respectivement la perception de la verticale avec ou sans indices visuels (test de la baguette et du cadre, RFT ; test de verticale visuelle subjective, VVS). Ces deux études ont montré que le déficit somesthésique diminuait la contribution du référentiel égocentré (axe corporel) à la perception de la verticale. En réponse, les patients présentent une plus grande dépendance au champ visuel et s’appuient donc préférentiellement sur le référentiel allocentré. Le second axe de travail visait à identifier les stratégies sensorielles adoptées par ces patients, et à évaluer les répercussions de celles-ci sur les mécanismes de régulation posturale. Ces questions ont été investiguées au moyen d’évaluations posturographiques approfondies, utilisant à la fois des paradigmes de perturbation sensorielle et de double tâche, ainsi que des analyses linéaires et non-linéaires. Nous avons ainsi observé que le déficit somesthésique des patients altérait la contribution de la proprioception musculaire aux mécanismes en charge de la régulation automatique de l’équilibre postural. Ces modifications dans la régulation posturale se répercutent par une augmentation du monitoring actif des oscillations posturales par le système nerveux central. En retour, les patients SEDh développent une visuodépendance, et mettent en place des stratégies adaptatives basées sur une rigidification des mécanismes correctifs à long terme. Enfin, deux études pilotes ont été conduites afin de tester l’effet de stratégies de remédiation proprioceptive, à savoir les orthèses somesthésiques et la reprogrammation sensorimotrice, sur le contrôle postural de ces patients. Chacune de ces prises en charge semble exercer un effet bénéfique sur leur contrôle postural, qui se traduit par une augmentation de la stabilité posturale lors du port des orthèses somesthésiques, et une amélioration de l’efficacité du contrôle postural suite à la reprogrammation sensorimotrice. Néanmoins, les résultats indiquent également que l’effet immédiat opéré par les dispositifs orthétiques de suppléance somesthésique est limité puisqu’il ne permet pas de diminuer la visuodépendance des patients. Cet effet est, en revanche, induit par l’action de la reprogrammation sensorimotrice, qui, par le renforcement du système proprioceptif, libère les patients SEDh de leur visuodépendance. Ainsi, ces observations nous ont permis de caractériser les spécificités de la régulation posturale chez les patients SEDh, et, de façon préliminaire, d’observer la façon dont celles-ci évoluent en réponse à des prises en charge spécifiquement orientées sur la remédiation sensorielle. / Ehlers-Danlos syndrome (EDS) is the clinical manifestation of hereditary connective tissue disorders, comprising several clinical forms. The EDS hypermobility type (EDSh) is characterized by generalized joint hypermobility and variable skin hyperextensibility, which both generate somatosensory impairment. Somatosensory system is, together with visual and vestibular systems, crucially involved in sensorimotor system functioning. The aim of this work was to understand the impact of impaired proprioception on perceptive and sensorimotor mechanisms underlying postural control in EDSh patients. Evaluation of postural control was structured around two approaches. The first one was indirect, and evaluated the sensory mechanism underlying vertical perception. The second one was direct, and used detailed stabilometric analyses to investigate postural control.The first objective of this work was to evaluate how somatosensory impairment affects the contribution of spatial frame of reference (allocentric, egocentric, and geocentric) to visual vertical perception. Two types of tests were conducted to assess the vertical perception with and without visual information (Rod and Frame Test, RFT; Subjective visual vertical, SVV). These two studies showed that somatosensory impairment reduces the contribution of egocentric frame of reference (body axis) to vertical perception. In response, patients increase their visual field dependence, and thus, use preferentially allocentric frame of reference. The second axis aimed to identify sensory strategies adopted by these patients and their repercussion on postural regulation mechanisms. To investigate this question, a thorough postural assessment was conducted, using sensory perturbation and dual-task paradigm, and linear and non-linear analyses. We observed that somatosensory impairment impacts muscular proprioceptive contribution to automatic regulation mechanism involved in postural control. These modifications in postural regulation induce an increase of active monitoring of postural sway. In response, EDSh patients develop a visual dependence, and produce adaptive strategies based on stiffening of corrective mechanisms acting in long term. Finally, two pilot studies were conducted to test the impact of proprioceptive remediation, somatosensory orthoses and sensorimotor rehabilitation program, on postural control of these patients. Both of these two therapeutic solutions seem to induce a beneficial effect on postural control. This effect is reflected by an improvement of postural stability when patients wore somatosensory orthoses, and an enhancement of postural efficiency in response to sensorimotor rehabilitation. However, results also indicate that the immediate effect induced by orthotic device of somatosensory substitution is limited, because it did not help to decrease visual dependency. Hence, these observations allowed us to identify the postural regulation specificities in EDSh patients, and, in a preliminary way, to observe how they change in response to therapeutic solutions based on sensory remediation.