Consciousness loss in patients with severe brain injuries is associated with reduced functional connectivity of the default mode network (DMN), fronto-parietal network, and thalamo-cortical network. However, it is still unclear if the brain white matter connectivity between the above mentioned networks is changed in patients with disorders of consciousness (DOC). In this study, we collected diffusion tensor imaging (DTI) data from 13 patients and 17 healthy controls, constructed whole-brain white matter (WM) structural networks with probabilistic tractography. Afterward, we estimated and compared topological properties, and revealed an altered structural organization in the patients. We found a disturbance in the normal balance between segregation and integration in brain structural networks and detected significantly decreased nodal centralities primarily in the basal ganglia and thalamus in the patients. A network-based statistical analysis detected a subnetwork with uniformly significantly decreased structural connections between the basal ganglia, thalamus, and frontal cortex in the patients. Further analysis indicated that along the WM fiber tracts linking the basal ganglia, thalamus, and frontal cortex, the fractional anisotropy was decreased and the radial diffusivity was increased in the patients compared to the controls. Finally, using the receiver operating characteristic method, we found that the structural connections within the NBS-derived component that showed differences between the groups demonstrated high sensitivity and specificity (>90%). Our results suggested that major consciousness deficits in DOC patients may be related to the altered WM connections between the basal ganglia, thalamus, and frontal cortex.

Parcellation of the orbitofrontal cortex, anterior cingulate cortex, and inferior frontal gyrus based on their functional connectivity with the whole brain in resting state fMRI with 654 participants was performed to investigate how these regions with different functions in reward, emotion and their disorders are functionally connected to each other and to the whole brain. The human medial and lateral orbitofrontal cortex, the ventromedial prefrontal cortex, the anterior cingulate cortex, and the right and left inferior frontal gyrus have different functional connectivity with other brain areas and with each other; and each of these regions has several parcels with different functional connectivity with other brain areas. In terms of functional connectivity, the lateral orbitofrontal cortex extends especially on the right into the orbital part of the inferior frontal gyrus and provides connectivity with premotor cortical areas. The orbitofrontal cortex, especially the lateral orbitofrontal cortex, has connectivity not only with language-related areas in the inferior frontal gyrus (Broca's area), but also with the angular and supramarginal gyri. In this context, whereas the connectivity of the orbitofrontal cortex, ventromedial prefrontal cortex, and anterior cingulate cortex is symmetrical, the connectivity of the inferior frontal gyrus triangular and opercular parts is asymmetrical for the right and the left hemispheres. These findings have implications for understanding the neural bases of human emotion and decision-making, and for their disorders including depression.

The cortical connections of the human hippocampal memory system are fundamental to understanding its operation in health and disease, especially in the context of the great development of the human cortex. The functional connectivity of the human hippocampal system was analyzed in 172 participants imaged at 7T in the Human Connectome Project. The human hippocampus has high functional connectivity not only with the entorhinal cortex, but also with areas that are more distant in the ventral 'what' stream including the perirhinal cortex and temporal cortical visual areas. Parahippocampal gyrus TF in humans has connectivity with this ventral 'what' subsystem. Correspondingly for the dorsal stream, the hippocampus has high functional connectivity not only with the presubiculum, but also with areas more distant, the medial parahippocampal cortex TH which includes the parahippocampal place or scene area, the posterior cingulate including retrosplenial cortex, and the parietal cortex. Further, there is considerable cross connectivity between the ventral and dorsal streams with the hippocampus. The findings are supported by anatomical connections, which together provide an unprecedented and quantitative overview of the extensive cortical connectivity of the human hippocampal system that goes beyond hierarchically organised and segregated pathways connecting the hippocampus and neocortex, and leads to new concepts on the operation of the hippocampal memory system in humans.