Dynamics, connectivity and anatomical-functional coupling during loss of consciousness in deep sleep

ENZO TAGLIAZUCCHI; NICOLAS CROSSLEY; EDWARD BULLMORE; HELMUT LAUFS

Chicago

Congreso; Society for Neuroscience Meeting; 2015

Daily, we experience deep sleep as a state of reversible loss of consciousness. Why is brain activity during sleep not associated with conscious awareness, and which mechanisms allow the re-emergence of wakefulness? In response, we derive three fundamental principles of deep sleep from electrophysiology-combined functional neuroimaging data: 1) In contrast to wakefulness, activity in frontoparietal regions exhibits random, uncorrelated dynamics; 2) Large-scale functional connectivity changes in this set of regions - compared to wakefulness - represent a localised departure from the underlying constraints imposed by anatomical connectivity; 3) A simple model unfolding over the network of anatomical connections can accommodate both observations above, provided that a change in the threshold for activity propagation occurs. Our results highlight network-specific, diminished complexity of spatiotemporal dynamics as a correlate of loss of consciousness. They also suggest that deep sleep actively disrupts default patterns of functional connectivity in associative cortices, which are essential for the conscious access of information, and that anatomical connectivity acts as an anchor for the restoration of frontoparietal functionality upon awakening. This last observation may be the key for the understanding of conditions characterized by an irreversible loss of consciousness like coma or the vegetative state.