Functional brain imaging and consciousness

Abstract

The neurobiological mechanisms underlying the maintenance of the conscious state have been extensively investigated with functional brain imaging techniques, in particular in relation to the alterations to consciousness associated with sleep and neurological and neuropsychiatric disorders. A consistent observation in these studies is the modification of activity and connectivity in distributed networks of cortical and subcortical brain regions, often associated with resting-state networks (RSNs). Several RSNs can be identified from functional imaging data, with separate networks associated with primary sensory domains and higher-level cognitive functions. One of the RSNs that has been consistently implicated in alterations to consciousness is the default mode network (DMN), with studies across diverse neurological and neuropsychiatric disorders identifying differences in DMN connectivity between control subjects and patients. While the data required to examine resting functional networks is easily acquired, and the functional networks themselves are reproducible and reliable, quantifying networks of distributed brain activity and identifying the most informative features in a particular disorder remains a challenge. Progress has been made in this direction in recent years, with the adoption of mathematical tools from network engineering, and the hope is that these methods will lead to additional techniques for the diagnosis and management of neurological and neuropsychiatric disorders of consciousness.