Sleep disconnection : EEG decoding of covert attention during different vigilance states

Sleep is a mystery for the conscious mind. Indeed, whilst being asleep, either consciousness is reduced and few memories remain upon awakening. Or consciousness is altered during dreams and memories struck us by their incongruity. What happens then when we sleep? In this thesis, we played complex sounds to study how the brain interprets information from the external world during sleep. We asked ourselves how the sleep disconnection from its sensory environment depends on cognitive processes occurring during sleep. To do so, we used EEG, a brain imaging technique. We could show that the sleeping brain keeps on monitoring sounds and can even selectively enhance or suppress certain information, as well as learn a foreign language. These capacities depend nevertheless crucially on markers of internal activity during sleep, demonstrating that sleep is a fundamentally active process and host of complex cognitive activit