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La conscience altérée : recherche de corrélats anatomo-fontionnels et étude de stimulation cérébrale profonde

Abstract : Consciousness can be divided into two major components: arousal and awareness. Awareness encompasses self-awareness and external awareness. Three core cerebral networks have been described. The default mode network is involved in self-related mental activity, and is internally-mediated. The central executive network is involved in externally-driven cognitive functions. The salience network is involved in the detection of salient internal and external stimuli, and plays a causal role in switching between the default mode and the central executive networks, thus mediating attention to internal and external worlds, respectively.Following a coma, some patients are left with chronic disorders of consciousness, either with unresponsive wakefulness syndrome, or in minimally conscious state. The unresponsive wakefulness syndrome is characterised by the absence of signs of awareness. The minimally conscious state is associated with minimal behavioural evidence of awareness, like visual pursuit or simple command following. The level of awareness can be underestimated by clinical assessment, owing to frequent motor and cognitive associated disorders.This thesis aims at improving awareness assessment via the detection of potential residual covert abilities, at characterising neural correlates of consciousness disorders, and at studying the effects of deep brain stimulation on conscious behaviour in patients with chronic disorders of consciousness.For the purpose of enhancing awareness detection in these non-communicative patients, we proposed a functional MRI protocol with graduated emotional charge to detect potential residual covert language-related behaviour. We then investigated the functional connectivity at rest of subcortical structures and cortical networks involved in internal and external awareness, in a group of thirteen patients with chronic disorders of consciousness. We highlighted a disruption of the functional connections between the salience and the default mode networks, as well as with the thalami and pallidums. We proposed beforehand a method to improve the automatic segmentation of these subcortical structures. Finally, we conducted a low frequency deep brain stimulation study in five patients with chronic disorders of consciousness, by dual pallido-thalamic targeting. Two patients showed improved conscious behaviour following stimulation, associated with an increase of metabolism in cortical regions involved in internal awareness.
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Anna Sontheimer. La conscience altérée : recherche de corrélats anatomo-fontionnels et étude de stimulation cérébrale profonde. Neurosciences [q-bio.NC]. Université Clermont Auvergne, 2019. Français. ⟨NNT : 2019CLFAS013⟩. ⟨tel-02498512⟩

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