Altered network properties of the fronto-parietal network and the thalamus in impaired consciousness

Recovery of consciousness has been associated with connectivity in the frontal cortex and parietal regions modulated
by the thalamus. To examine this model and to relate alterations to deficits in cognitive functioning and
conscious processing, we investigated topological network properties in patients with chronic disorders of consciousness
recovered from coma.
Resting state fMRI data of 34 patients with unresponsive wakefulness syndrome and 25 in minimally conscious
state were compared to 28 healthy controls.We investigated global and local network characteristics. Additionally,
behavioralmeasureswere correlatedwith the localmetrics of 28 regionswithin the fronto-parietal network
and the thalamus.
In chronic disorders of consciousness, modularity at the global level was reduced suggesting a disturbance in the
optimal balance between segregation and integration.Moreover, network properties were altered in several regionswhich
are associatedwith conscious processing (particularly, inmedial parietal, and frontal regions, aswell
as in the thalamus). Between minimally conscious and unconscious patients the local efficiency of medial parietal
regions differed. Alterations in the thalamus were particularly evident in non-conscious patients.Most of the regions
affected in patientswith impaired consciousness belong to the so-called ‘rich club’ of highly interconnected
central nodes. Disturbances in their topological characteristics have severe impact on information integration and
are reflected in deficits in cognitive functioning probably leading to a total breakdown of consciousness.