Consciousness, Functional networks and Delirium screening.

Consciousness, the medium of sentient thought, requires integrity of functional networks and their connectivity. In health, they function as a co-operative but mutually exclusive paradigm of introspection versus external awareness subserved via the Default Mode Network and Task Positive State respectively. Higher thinking is segregated according to need, but this relationship is impacted in disorders of consciousness. In delirium, a disturbance of consciousness, the Default Mode Network is pathologically co-activated and functional cortical connectivity is compromised. Inversion of this functional network relationship in conjunction with cortical disconnectivity, we argue, is central to the mechanism of delirium. The corollary of divided networks is that internal and external drivers become indistinguishable, and an experiential singularity follows where reality and delusion merge and the notion of self is effaced. Clinical tools may exploit the neurobiology of delirium to improve diagnosis and an example of such a screening instrument is provided.