Abstract :
[en] Consciousness is a phenomenon that has so far evaded detailed description. However, with the help of modern brain imaging techniques, we can examine some of the mechanisms underlying changes in its prominence. In the experiments described in this thesis, we used structural and functional magnetic resonance imaging to discover new brain alterations occurring during two types of loss of consciousness: pharmacological (propofol anesthesia) and pathological (disorders of consciousness: vegetative state/unresponsive wakefulness syndrome, in which no awareness is assumed, and minimally conscious state, with fluctuating low-level consciousness). In both cases, we found loss of consciousness to be associated with a breakdown of three brain networks involved in higher-order processing: the default mode network, external control network, and salience network. These networks have been associated with internal awareness, external awareness, and saliency detection, respectively. Furthermore, their connectivity with the thalamus was severely disrupted. Our findings suggest that these changes could be a general hallmark of loss of consciousness. Additionally, we developed several novel techniques to examine changing brain dynamics, which could be used to search for other mechanisms underlying loss of consciousness. In contrast to anesthesia, loss of consciousness in patients with disorders of consciousness is the result of structural brain damage. We performed an analysis of white and gray matter damage occurring in these patients and found it to be widespread, with damage in midline default mode network regions potentially discriminating between unconscious and conscious patients.Our results indicate that structural and resting state functional magnetic resonance imaging might have the potential to improve differential diagnosis in disorders of consciousness.
