Functional and structural brain connectivity in disorders of consciousness

Abstract Objective: Brain connectivity, allowing information to be shared between distinct cortical areas and thus to be processed in an integrated way, has long been considered critical for conscious access. However, the relationship between functional intercortical interactions and the structural connections thought to underlie them is poorly understood. In the present work, we aim to explore this structure-function relationship in patients with disorders of consciousness, and to investigate the interest of exploring both types of connectivity for clinical diagnosis. Methods: We explore both functional (with an EEG-based metric: the median weighted symbolic mutual information in the theta band) and structural (with a brain MRI-based metric: fractional anisotropy) connectivities in a cohort of 78 patients affected with a disorder of consciousness. Results: Both metrics could distinguish patients in a vegetative state from patients in minimally conscious state. Crucially, we discovered a significant positive correlation between functional and structural connectivities. We then showed that this structure-function relationship takes place in the long-range cortico-cortical deep white matter bundles involved in the Global Neuronal Workspace theory of consciousness. Interpretation: Altogether, these results support the interest of a multimodal assessment of brain connectivity to refine the diagnostic and prognostic evaluation of patients with disorders of consciousness.