Theta network centrality correlates with tDCS response in disorders of consciousness

Transcranial direct current stimulation (tDCS) applied over the dorsolateral prefrontal cortex (DLPFC) has induced promising behavioral improvement, both in acute and chronic minimally conscious state (MCS - [ 1 ]) patients [ 2 , 3 ]. We previously defined a tDCS-responder as a patient who demonstrates a new sign of consciousness following stimulation, which was neither present beforehand, nor before or after the sham stimulation [ 2 ]. In a study investigating the metabolic and structural differences between DLPFC-tDCS-responders and non-responders, we have identified that tDCS-responders presented a preservation of brain metabolism and grey matter integrity under the stimulated area, but also in the thalamus and the precuneus, areas involved in consciousness recovery [ 4 ]. Even if these results provided relevant insights into potential biomarkers of responsiveness, the access to such neuroimaging techniques (positron emission tomography - PET - and magnetic resonance imaging - MRI) remains limited. Recently, it has been demonstrated that high-density electroencephalography (hdEEG) network metrics in the alpha band correlates with the level of consciousness [ 5 ]. In addition, a strong correlation between brain metabolism and hdEEG network metrics was reported, making this bedside assessment a robust way to evaluate patients’ brain function.