Limbic hyperconnectivity in the vegetative state

Objective: To investigate functional connectivity between the default mode network (DMN) and other networks in disorders of consciousness. Methods: We analyzedMRI data from 11 patients in a vegetative state and 7 patients in a minimally conscious state along with age- And sex-matched healthy control subjects. MRI data analysis included nonlinear spatial normalization to compensate for disease-related anatomical distortions. We studied brain connectivity data from resting-state MRI temporal series, combining noninferential (independent component analysis) and inferential (seed-based general linear model) methods. Results: In DMN hypoconnectivity conditions, a patient's DMN functional connectivity shifts and paradoxically increases in limbic structures, including the orbitofrontal cortex, insula, hypothalamus, and the ventral tegmental area. Conclusions: Concurrently with DMN hypoconnectivity, we report limbic hyperconnectivity in patients in vegetative and minimally conscious states. This hyperconnectivity may reflect the persistent engagement of residual neural activity in self-reinforcing neural loops, which, in turn, could disrupt normal patterns of connectivity. © 2013 American Academy of Neurology.