Agency in Walking Humans Sensorimotor & [and] Cognitive Contributions to Bodily Self-Consciousness

Acting in our environment and experiencing ourselves as conscious agents are fundamental aspects of human selfhood. While large advances have been made with respect to understanding human sensorimotor control from an engineering approach, knowledge about its interaction with cognition and the conscious experience of movement, i.e. the sense of agency, is still speculative. In this thesis I have investigated these relationships by implementing a Virtual Reality platform, which allowed me to adapt agency paradigms previously limited to movements of individual body-parts to continuous full-body movements, i.e. locomotion. In a series of behavioural studies I investigated how a) spatial and b) temporal sensorimotor mismatches between participants' veridical gait-movements and their life-size visual feedback affected agency and gait. Our results illustrate that humans monitor the details of their movements and their location in space with surprisingly low accuracy. Participants did not become aware of sensorimotor mismatches below 15° and temporal mismatches of 210 ms, even though they automatically adapted their movements. These data confirm that gait and gait agency are distinct brain processes, that these can further be separated by taxing cognitive resources in dual task paradigms, and that they are comparable to agency mechanisms that have been described for upper limb movements. Together, these studies help to investigate sensorimotor components of selfhood that are of scientific, clinical, and legal relevance.

Agency, gait and self-consciousness

Olaf Blanke, Oliver Alan Kannape

Agency is an important aspect of bodily self-consciousness, allowing us to separate own movements from those induced by the environment and to distinguish own movements from those of other agents. Unsurprisingly, theoretical frameworks for agency such as central monitoring are closely tied to computational models of sensorimotor control. Until recently agency research has largely focussed on goal-directed movements of the upper limbs. In particular, the influence of performance-related sensory cues and the relevance of prediction signals for agency judgements have been studied through a variety of spatio-temporal mismatches between movement and the sensory consequences of movement. However, agents often perform a different type of movement; highly automated movements that involve the entire body such as walking, cycling, and swimming with potentially different agency mechanisms. Here, we review recent work about agency for full-body movements such as gait, highlighting the effects of performance-related visual and auditory cues on gait agency. Gait movements differ from upper limb actions. Gait is cyclic, more rarely immediately goal-directed, and is generally considered one of the most automatic and unconscious actions. We discuss such movement differences with respect to the functional mechanisms of full-body agency and body-part agency by linking these gait agency paradigms to computational models of motor control. This is followed by a selective review of gait control, locomotion, and models of motor control relying on prediction signals and underlining their relevance for full-body agency.

2012

Manipulation of the participants' self-localization in a lying position

Michaël Mouthon

Healthy human beings are aware of their current position space and are able to distinguish their own body from that of other persons or objects. This capability arises from a coupling of sensory information with cognitive processes, and leads to a representation of the person's self. However, in some clinical cases these processes fail and a person can feel himself to be outside of his physical body, as in the out-of-body experience. These phenomena are interesting to study as they lend insight to certain aspects of bodily self-consciousness, such as self-localization and self-attribution. These aspects can be experimentally manipulated in healthy participants through exposure to conflicting multisensory input, as has been demonstrated with the creation of an ownership's feeling with rubber hand stroked synchronously with the real hand. Here, we worked on the full body by manipulate the self-localization of healthy participants. We used similar protocols as in the study of Lenggenhager et al. (2007) and Ehrsson (2007b) but with a lying position, rather a seated or standing as in the aforementioned studies, which are the commune position when out-of-body experience occurs. Participants were put in a comfortable lying position and saw an image of their body through 3D head mounted display, recorded by a video camera located two meters above them. By providing different temporal and spatial information about a visual-tactile event (stroking on the participants' back or chest) self-localization and identification could be modified in a predictable way. We measured self-localization using a mental ball dropping task and measured phenomenological aspects using a questionnaire. The results indicated that a significant variations in self-localization occurred during the experiment. As a follow-up study, we used mental imagery (in our case we used fMRI) to study the regions of the brain involved in this illusion

2008

The Rhythm of Bodily Self-Consciousness

Pär Halje

Recent philosophical, psychological and neuroscientific theories suggest that bodily experience is crucial for the phenomenology of selfhood (i.e. the experience of 'being someone'). In this thesis I have shown that two essential aspects of bodily self-consciousness that have been difficult to study in the past – self-location ('where am I localized?') and self-identification ('is this my body?') – can be manipulated experimentally with multisensory visual-tactile conflicts and virtual reality technology. A major part of this thesis was devoted to investigate how such manipulations are reflected in the oscillatory cortical resting state known as the mu rhythm. Through the mu rhythm I have also established a link between the mirror neuron system, self-other discriminations and cerebral speech representations of actions.

EPFL2010

Manipulation of the participants' self-localization in a lying position

Michaël Mouthon

2008