My thesis explores the interplay between perceptual awareness, metacognition and metarepresentations using various experimental manipulations. It is articulated around two approaches. 
The first part of my thesis seeks to better understand how perceptual awareness and metacognition are modulated by experimentally-induced metarepresentations in two studies based on beliefs manipulation. We use placebo suggestions aiming at improving perceptual awareness at different levels of processing in a first set of visual experiments and we study the impact of a negative placebo suggestion impact on perceptual awareness and metacognitive abilities in a second set of tactile experiments. Ours results suggest that placebo suggestions lead to fragile if not non-existent effects in non-noxious perception and that high-level cognitive-affective components may be essential for placebo effect to occur. The second part is focused on the relationship between perceptual consciousness and a core metarepresentation that is the self. In particular, it aims at deepening our understanding of whether bodily self-consciousness has a role in shaping perceptual consciousness. This fundamental relation has indeed surprisingly remained overlooked so far, perceptual- and bodily self- consciousness being largely studied independently. This second part is composed of 3 studies. The first one examines how body movement can influence vision and metacognition through sensory attenuation. The second study investigates how manipulating one’s sense of self through sensorimotor conflicts alters perception and metacognition. The third study explores whether self-metacognition requires embodiment and to which extent one can evaluate the (un)certainty of others. Taken together, our findings suggest that the brain — and consciousness — cannot be studied in isolation, and that it is essential to take into account our body and our actions into the world, as well as the fact that we live in a social environment in order to have a deeper understanding of perceptual consciousness. / Doctorat en Sciences psychologiques et de l'éducation / info:eu-repo/semantics/nonPublished

Dans la partie introductive de cette thèse sont illustrés le cadre théorique dans lequel se situent les études sur la reconnaissance du soi corporel. En outre, ce chapitre traite de la façon dont la reconnaissance visuelle des visages et des corps, et de la spécificité de la reconnaissance de son propre visage et de son propre corps, s’effectuent. Le deuxième chapitre décrit une étude menée chez des sujets sains, qui examine l'excitabilité du cortex moteur primaire dans le processus de reconnaissance de soi et de l’autre. Le troisième chapitre illustre l'expérience réalisé pour étudier la contribution du mouvement dans la reconnaissance du soi corporel chez des sujets neurologiquement sains et chez les patients avec lésion cérébrale de l’hémisphère droit. Le quatrième chapitre porte sur le développement du soi corporel chez les enfants avec un développement atypique, souffrant de troubles du spectre autistique à haut fonctionnement, avec une attention particulière au rôle des émotions dans la reconnaissance de postures émotionnels, propres et autrui. Enfin, le cinquième chapitre est consacré au rôle du geste dans la reconnaissance du propre corps et celui des autres / The first chapter describes the theoretical framework of self-body recognition and the processing that allow us to distinguish one’s own body and face from body and face of someone else. The second chapter will investigate motor cortex excitability during self/other recognition processing in healthy subjects. The results show an increment of motor corticospinal excitability in the right hemisphere following the presentation of self stimuli (hand and phone), at 600 and 900 ms after stimulus presentation, providing evidences about neural substrates and temporal processes underlying self-body recognition. The third chapter will describe the role of the movement in self bodily recognition in healthy subjects and in patients with right brain damage. The evidence show that patients, who did not show the advantage in the implicit recognition of self static body parts, present this advantage in the implicit recognition of self dynamic body parts. The fourth chapter focuses on the development of the bodily self in children with typical development and in children with autism, with respect to the recognition of self/other emotional body postures. First, this study shows that the advantage in bodily self processing is preserved in children with autism. Second, emotional body postures modulated self and others body processing in typically developing children, as well as in children with autism. The fifth chapter deals with the role of hand gestures in self/other bodily recognition processing, showing that the meaning of a gesture modulates the self/other processing. The processing of others’ hand is facilitated with meaningful compared to meaningless gestures

In the last decade, neuroscience and psychology alike have paid increasing attention to the study of affective touch, which refers to the emotional and motivational facets of tactile sensation. Some aspects of affective touch have been linked to a neurophysiologically specialised system, namely the C tactile (CT) system. While the role of this system for affiliation, social bonding and communication of emotions have been investigated, less is known about the potential role of affective touch in the awareness of the body as our own, i.e. as belonging to our psychological 'self'. This thesis attempted to contribute to the knowledge on affective touch and its relation to body awareness, by exploring the potential role of this modality to the way we perceive and make sense of our body as our own. Specifically, this work aimed to advance the current state of knowledge by investigating: 1) the effect of affective touch on the sense of body ownership, which is a fundamental aspect of body awareness; 2) the relation between interoceptive modalities, originating both internally (i.e. cardiac awareness) and peripherally (i.e. affective touch), and exteroception in body awareness; 3) the effect of intranasal oxytocin on the perception of affective touch and bodily awareness; 4) the perception and social modulation of affective touch in psychiatric patients who show difficulties in body awareness, namely patients with Anorexia Nervosa, and 5) the modulating role of self-other distinction and of self-other relation in the perception of affective touch and body awareness. In a first experiment (N = 52) the rubber hand illusion paradigm was used to investigate the role played by CT-optimal, affective touch in the sense of body ownership. The results showed that slow, pleasant touch enhanced the experience of embodiment in comparison to faster, neutral touch, suggesting that affective touch might uniquely contribute to the sense of body ownership. The following study (N = 75), used a similar methodology to test whether interoceptive sensitivity as measured by a heartbeat counting task would modulate the extent to which affective touch influences the multisensory process taking place during the rubber hand illusion. The results could not confirm a systematic relation between interoceptive sensitivity and the perception of affective touch, nor its influence on body ownership. The next study (N = 41) included a double-blind, placebo-controlled, randomised, cross-over design testing the effect of intranasal oxytocin on the perception of affective touch and body ownership, as measured by means of the rubber hand illusion. There was no evidence supporting the hypothesis that intranasal oxytocin could influence the CT system as tested in this study. The next study (N = 55) applied some of the above methodologies to investigate the perception of CT-optimal touch in patients with anorexia nervosa and its emotional modulation by top-down factors. The results confirmed the hypothesis that people with anorexia nervosa show a reduced perception of affective touch compared to healthy controls, but its perception was not influenced by top-down affective modulation, in the sense that both patients and healthy controls perceived touch as more pleasant when presented concurrently with positive facial expressions compared to neutral and negative faces. Finally, the last two studies (N = 76 and 35 healthy volunteers, respectively) focused on the relationship between affective touch and body awareness in the context of social cognition. These studies used both online and offline social modulation paradigms to investigate the role of self-other distinction and of self-other relation in the perception of affective touch. The results showed that positive top-down social information can enhance the perceived pleasure of tactile stimulation. Taken together, these studies point to the central role of affective touch in body awareness and social cognition. Finally, they also pave the way for future studies examining the role of disruptions of the CT system in the development of neuropsychiatric impairments of body awareness and social cognition.

Ce travail a pour but de décrire les relations réciproques entre prise de perspective et informations vestibulaires. Une étude chez des patients avec un déficit vestibulaire bilatéral ancien et des sujets contrôles a montré que l’ancrage du soi sur le corps et la simulation implicite de la perspective visuo-spatiale d’autrui étaient similaires chez les deux groupes. Ainsi, une perte vestibulaire ancienne n’entraînerait pas de conflits multisensoriels, connus pour évoquer un sentiment de perspective désincarnée chez des patients avec des déficits vestibulaires aigus. Une étude chez des volontaires sains a combiné des stimulations vestibulaires naturelles sur fauteuil rotatoire à des tâches de prise de perspective dans un environnement virtuel embarqué. Les temps de prise de perspective étaient modulés en fonction de la direction de la rotation. Cette influence n’était pas présente pour la rotation mentale d’objets 3D. La contribution vestibulaire canalaire modulerait donc spécifiquement les rotations mentales du point de vue. Enfin, les modulations cognitives du traitement des informations vestibulaires ont été analysées par l’enregistrement de potentiels évoqués myogéniques vestibulaires sur les muscles sternocléidomastoïdiens et trapèzes. L’amplitude des potentiels évoqués était significativement modulée par l’angle séparant le point de vue du participant et celui d’un avatar distant. Nos travaux théoriques et les résultats de cette série d’expériences démontrent la contribution des informations vestibulaires à la prise de perspective visuo-spatiale. / This thesis aims at describing the reciprocal relations between perspective taking and the vestibular system. A study in patients with bilateral vestibular deficits and controls showed that the anchoring of the self to the body and implicit visuo-spatial perspective taking were similar in both groups. Our negative findings offer insight into the multisensory mechanisms of embodiment: only acute peripheral vestibular disorders and neurological disorders in vestibular brain areas may evoke disembodied experiences. A second study, combined natural vestibular stimulation on a rotatory chair with virtual reality to test how vestibular signals are processed to simulate the view point of a distant avatar. While they were rotated, participants tossed a ball to a virtual character from the view point of a distant avatar. Our results showed that participants were faster when their physical body rotated in the same direction as the mental rotation needed to take the avatar's viewpoint. Altogether, these data indicate that vestibular signals have a direction-specific influence on visuo-spatial perspective taking, but not a general effect on mental imagery. Finally, cognitive modulations of vestibular information processing were analyzed by recording vestibular-evoked myogenic potentials on the sternocleidomastoid and trapeze muscles. The amplitude of evoked potentials was significantly modulated by the angle separating the participant’s viewpoint to that of a distant avatar. To conclude, our theoretical work, together with results from this series of experiments, demonstrate the contribution of vestibular information to visuo-spatial perspective taking.