Abstract
Severe brain injury may cause disruption of neural networks that sustain arousal and
awareness, the two essential components of consciousness. Despite the potentially
devastating immediate and long-term consequences, disorders of consciousness (DoC)
are poorly understood in terms of their underlying neurobiology, the relationship
between pathophysiology and recovery, and the predictors of treatment efficacy. Recent
advances in neuroimaging techniques have enabled the study of network connectivity,
providing great potential to improve the clinical care of patients with DoC. Initial
discoveries in this field were made using positron emission tomography (PET). More
recently, functional magnetic resonance (fMRI) techniques have added to our understanding
of functional network dynamics in this population. Both methods have shown that whether
at rest or performing a goal-oriented task, functional networks essential for processing
intrinsic thoughts and extrinsic stimuli are disrupted in patients with DoC compared
with healthy subjects. Atypical connectivity has been well established in the default
mode network as well as in other cortical and subcortical networks that may be required
for consciousness. Moreover, the degree of altered connectivity may be related to
the severity of impaired consciousness, and recovery of consciousness has been shown
to be associated with restoration of connectivity. In this review, we discuss PET
and fMRI studies of functional and effective connectivity in patients with DoC and
suggest how this field can move toward clinical application of functional network
mapping in the future.
Keywords
brain injury - coma - consciousness - network - connectivity - fMRI - PET - neuroimaging
