Dyspraxie | EPFL Graph Search

La dyspraxie, aussi appelée trouble développemental de la coordination (TDC), trouble d’acquisition de la coordination (TAC) ou dyspraxie développementale (DD), est un trouble neurologique chronique qui apparaît dès l'enfance. Ce trouble spécifique des apprentissages (TSAp) (terminologie APA, 2013) se caractérise par une affection de la planification des mouvements et de la coordination en raison d'une altération de la communication entre le cerveau et le corps. Ce trouble se caractérise en particulier par une altération de la capacité à exécuter de manière automatique des mouvements déterminés, en l'absence de toute paralysie ou parésie des muscles impliqués dans le mouvement. Le sujet doit contrôler volontairement chacun de ses gestes, ce qui est très coûteux en attention, et rend la coordination des mouvements complexes de la vie courante extrêmement difficile, donc rarement obtenue. C'est une apraxie d'origine développementale. Les déficiences de l'habileté chez l'enfant interf

Collective search of a single odour source using cooperation

Alexandre Herrmann

We study coordination strategies for a multirobot team. The goal is to find the source of an odour most efficiently in terms of the distance travelled by the robots and the time required to discover the source. We focus on the problem of finding the source of the odour once a robot has already found the plume of this odour. The results show that the studied algorithms are effective in non-homogeneous wind models, which include turbulences.

2007

In vitro endoderm emergence and self-organisation in the absence of extraembryonic tissues and embryonic architecture

Stefano Davide Vianello

In humans, mice, and other mammals key internal organs such as the gut, the lungs, the pancreas, and the liver all derive from the same embryonic tissue: the endoderm. The development of all of these structures thus depends on a same set of early cells, and on the developmental instructions provided to them by the embryo. One approach to study what these instructions might be is to study the behaviour of endoderm cells when they can not rely on embryonic instructions. That is, when they are generated and made to develop outside of the embryo. The rationale behind this approach, widely embraced by the field of synthetic embryology, is that the unguided development of specific embryonic cell types can provide a window to the observation of intrinsic characteristics of these cells and of fundamental developmental principles which might not be executed or manifested within the regulated environment of the embryo. Accordingly, in the work here described I use gastruloids, synthetic models of development made by aggregation of mouse embryonic stem cells in vitro to characterise the developmental behaviour of endoderm cells, in the absence of embryonic cues and in the absence of the extraembryonic tissues that they would usually rely on in vivo. In the first chapter of this thesis, I provide an introduction, overview, and review of our current understanding of the developmental biology of mouse endoderm as this develops in the embryo. I also introduce gastruloids as stem-cell-based experimental systems to study developmental mechanisms in vitro, decoupled from the constraints of experimental work with animals and animal embryos. Chapter 2 is dedicated to the earliest steps of endoderm development in gastruloids. I show when and where these cells appear, and how they sort as the gastruloid starts to mature. I find that endoderm cells follow similar spatial and temporal developmental patterns as those they would follow if they were in the embryo. I notably find that they always remain in an epithelial state, even as other cell types undergo mesenchymal transition. In Chapter 3 I describe surprising dynamics of endoderm cells over time, and how they self-organise into complex architectures at the core of the gastruloids. The epithelial domain that forms is dynamic and plastic, and partitions the gastruloids into interfacing compartments. Importantly, I reveal a significant endodermal component to this in vitro system, usually considered to be unstructured and neural/mesodermal in character. In Chapter 4 I show how the core endoderm compartment that I see forming in gastruloids is patterned along the longitudinal axis of the aggregate, with different cellular identities at different anterior-posterior position of the domain. By comparison with published embryonic datasets, I identify endodermal identities corresponding to the full spectrum of those that make up the gut tube in the embryo. Specifically, I describe how most endodermal cells adopt an early intestinal fate, and how many acquire anterior foregut identities. The work described in this thesis presents gastruloids as promising in vitro systems for the study of endoderm biology, morphogenesis, and mature fate specification, filling a gap within the field of synthetic embryology. It also notably opens translational possibilities to the use of gastruloids to produce endodermal cell types which may be otherwise difficult to generate using conventional directed differentiation methods.

EPFL2022

The variability of contact position errors in apraxic imitation

Aude Billard, Biljana Petreska von Ritter-Zahony

Apraxia is a poorly understood disorder of voluntary movement that is not due to basic sensory, motor or cognitive deficits. We conducted a study on the imitation of meaningless gestures in apraxic patients with left fronto-temporo-parietal lesions. In a first condition, the patients were instructed to imitate the orientation and position of a hand touching the face (complex task). In a second condition, the patients were instructed to solely imitate the position of contact between the face and hand, using any orientation of the hand (simple task). We did not observe contact position errors (CPEs) in the simple task, which argues in favor of preserved spatial and motor representations of the body. However, the patients made a substantial amount of CPEs in the complex task, indicating a misuse of these spatial and motor representations of the body when the task involved several imitation goals (e.g. the thumb touches the nose and the hand is oriented vertically). The error variability was remarkably low across trials. Most of the CPEs could be explained by an incorrect coordination between the reproductions of multiple imitation goals. If simple movements are easier to imitate and less prone to errors, an efficient rehabilitation therapy may use movements of increasing complexity.

2010

In vitro endoderm emergence and self-organisation in the absence of extraembryonic tissues and embryonic architecture

Stefano Davide Vianello

EPFL2022