The cognitive processing of a stimulus does not only depend on the physical properties of the stimulus itself but also on the larger context in which it occurs. In this thesis I will present a number of studies that investigate this context-dependency at different levels of cognition. In particular these levels include (1) sensory processing within a modality, (2) sensory integration across modalities and (3) the relation between sensory perception and motor behavior. Accordingly the chapters in this thesis are partitioned into three larger parts, each of which relates to one of these levels. The first study in Part 1 investigates the role of neural oscillations during perceptual grouping. By measuring EEG during contour integration we were not only able to identify the neural sources involved in this process but also to demonstrate local and long-range synchronization of oscillatory activity within frontoparietal networks. This study is then followed by a more general discussion about the properties of oscillatory activity and how they might relate to event-related potentials. The focus of Part 2 will then be on cross-modal interactions and their possible utilization for real-life applications. First we show that simultaneously presented auditory and tactile cues lead to interactions on both a behavioral and neural level. Subsequently we demonstrate how the observed perceptual effects can be used to optimize auditory and tactile localization performance. Finally we propose a setup for utilizing tactile information to enhance the perceptual interpretation of 360° visual scenes. The third and last part of this thesis is dedicated to problems and applications of measuring EEG in the presence of eye movements. Therefore we use eye tracking to investigate and characterize EEG artifacts resulting from ocular activity. Subsequently we develop an algorithm that allows objectively and reliably identifying these artifacts and removing them from the data without affecting the signal from neural sources. Employing this algorithm we then demonstrate that combined EEG and eye tracking can be used for monitoring and shaping both the gaze behavior and the related brain activity in ASD patients. Next to studying cognition with regard to perceptual and behavioral context, this thesis also focuses on the question how the context-relevant signal components can be identified and extracted from the EEG. In the studies presented here we applied a variety of different strategies to approach this problem. These range from resorting to prior knowledge and analyzing only activity from predetermined cortical sources on the one hand, to purely data driven approaches based on logistic regression or eye tracking information on the other hand.

La maladie de Parkinson induit des troubles locomoteurs complexes et variés. Des troubles spécifiques de la marche tels que le " freezing " peuvent survenir ponctuellement. Afin d'améliorer l'accompagnement de ces patients, il est nécessaire d'améliorer notre compréhension de ces situations. Cette thèse vise à caractériser l'activité locomotrice des patients parkinsoniens en situation réelle. Un travail interdisciplinaire a été mené, fondé sur une approche écologique. Quatorze patients ont été suivis. La méthode déployée intégrait le recueil de marqueurs biomécaniques et physiologiques, de l'expérience vécue ainsi que des observations directes. La description de leur expérience a révélé une perception sensori-motrice altérée et une organisation du comportement locomoteur spécifique à l'environnement. Les analyses montrent un schéma d'activation musculaire spécifique, avec notamment une prolongation générale de l'activité des muscles pendant la phase d'appui simple et une augmentation de cocontraction lorsque le pied est en contact au sol. Les résultats de cette analyse intégrée du comportement moteur ont permis de caractériser une typologie de cinq marches et de trois types de " freezing ". De plus, ces observations ont mis en valeur des stratégies utilisé par des patients ainsi qu'un mécanisme d'ajustement neuromusculaire pour augmenter la stabilité de la marche. A long terme, ce travail devrait favoriser 1) la compréhension des bases neurologiques des troubles de la marche ; 2) la prise en charge des patients parkinsoniens ; 3) l'identification des biomarqueurs de la stabilité de la marche ; 4) la spécification des systèmes embarqués du suivi de la marche. / Patients with Parkinson’s disease (PD) experience complex locomotor disturbances. Their walking abilities can be highly variable and specific problems such as freezing of gait may arise during daily life activity. A greater understanding of such difficulties is required in order to develop new therapeutic strategies. This thesis examines the emergence of PD gait patterns during everyday situations. To this end, this study used an interdisciplinary approach drawing upon ecological and embodied perspectives of human activity. The investigation focused upon fourteen PD patients. Data collection methods combined interviews, direct observations and onboard measures of physiological and biomechanical performance. This research identified important changes in patient sensorimotor perception during gait and specific principles regarding the organisation of their movements with respect to the environment. Analysis revealed characteristic changes to lower limb muscle activation patterns, most notably the prolongation of muscle activity during the mid-stance phase; and an increase in cocontraction of agonist-antagonist muscles across the ankle and knee whilst the leg was in contact with the ground. This integrated approach enabled the characterisation of five walking patterns and three types of freezing. These results highlighted patient self-management strategies, and indicated the role of neuromuscular mechanisms for increasing gait stability. Ultimately, these findings may assist to 1) understand the neurological bases of gait dysfunction; 2) enhance PD patient care; 3) identify biomarkers for gait stability and; 4) support the development of ambulatory monitoring technologies.

The purpose of this project is to argue that we possess a minimal self. It will demonstrate that minimal selfhood arrives early in our development and continues to remain and influence us throughout our entire life. There are two areas of research which shape my understanding of the minimal self: phenomenology and enactivism. Phenomenology emphasizes the sense of givenness, ownership, or mineness that accompanies all of our experiences. Enactivism says there is a sensorimotor coupling that occurs between us and the environment in a way which modulates the dynamic patterns of our self development; the laying down of these basic patterns helps make us who we are and gives rise to the phenomenological, experiential mineness. Drawing on these two core ideas, I will be arguing for a Phenomenological-Enactive Minimal Self (abbreviated PEMS). I will be emphasizing the role of the body and the role of affects (moods, feelings, and emotions) as the most important components relevant to understanding minimal selfhood. Put more concretely, the set of conditions which constitute the PEMS view are: (i) The minimal self is the experiential subject; the minimal sense of self is present whenever there is awareness. It is the subjectivity of experience, the sense of mineness, or givenness which our experiences contain. (ii) The phenomenological part of the PEMS view turns on the idea of a bodily and dynamic integration of sensorimotor coupling and affective experience. It is, ontologically speaking, the lived body in enactive engagement with the environment. It is this embodied subject which anchors and forms the foundation for the later ‘narrative' self, which emerges from it and which is continually influenced by it. It is the subject enactively engaged with others, dependent on sensorimotor processes and affects. We have an identity, but it emerges from relational and dynamic processes.