Resting functional connectivity in minimally conscious state minus and plus

Patients in a minimally conscious state (MCS) have been subcategorized in MCS plus and MCS minus, that is, with or without command following capacity respectively. We aimed to characterize this residual capacity in both patient groups by means of resting state fMRI. We hypothesized a higher connectivity in MCS plus as compared with MCS minus in language-related networks, that is the left fronto-parietal network (FPN). Our sample includes 10 MCS plus and 9 MCS minus who match for age, gender, etiology and disease duration, as well as 35 healthy controls. We performed a seed-based resting state analysis using CONN toolbox2. We investigated the left FPN, and also the right FPN, the auditory network and the default mode network (DMN) in order to exclude the influence of perception of surrounding, auditory capacity, or internal thoughts. We employed a ROI-to-ROI analysis to investigate the inter-hemispheric connectivity and we investigated inter-group differences in grey and white matter volume by means of voxel-based morphometry (VBM). We observed a higher functional connectivity in controls than in patients, as well as in MCS plus as compared to MCS minus patients. Specifically, with DLPFC as seed, the left FPN was more connected in MCS plus patients to the left temporo-occipital fusiform cortex. No significant differences were found between both patient groups in the right FPN, the auditory network and the DMN, or using the ROI-to-ROI analyses and the VBM. Our results suggest that the clinical sub-categorization of MCS is sustained by functional connectivity differences in a language-related executive control network. MCS plus and MCS minus patients are not differentiated by networks involved in auditory processing, perception of surroundings and internal thoughts, nor by inter-hemispheric connectivity and morphology.