Background: 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 in the conscious state is then segregated
according to need. There is research evidence to suggest that functional networks may be
impacted in disorders of consciousness and conceptual support for a mechanistic role in delirium.
This potentially central aspect of delirium manifestation is relatively unexplored.
Objective: This article describes the role of disrupted functional networks in delirium. How this relates
to current understanding of delirium neurobiology and the ramifications for clinical diagnosis
Method: A review of the role of functional networks, particularly DMN and TPN, has been undertaken
with respect to health and delirium. An exploration of how symptoms of delirium may be related
to functional network aberrancy has been undertaken. Implications for research and clinical
practice in delirium have been presented.
Results: In delirium, a disturbance of consciousness, the DMN is pathologically co-activated and
functional cortical connectivity is compromised. The clinical correlate is of an experiential singularity
where internal and external drivers become indistinguishable, reality and delusion merge and
the notion of self is effaced. Our group propose that functional network disruption in conjunction
with cortical disconnectivity is central to the mechanism of delirium. Clinical tools may exploit the
neurobiology of delirium to improve its diagnosis and an example of such a simple screening instrument
(SQeeC) is provided.
Conclusion: Functional networks are critically disrupted in delirium and may be central to clinical
features. A better understanding of the neurobiology of delirium will generate research opportunities
with potential for therapeutic gains in detection, diagnosis, and management.