tDCS modulates effective connectivity during motor command following; a potential therapeutic target for disorders of consciousness

Transcranial direct current stimulation (tDCS) is attracting increasing interest as a potential therapeutic route for unresponsive patients with prolonged disorders of consciousness (PDOC). However, research to date has had mixed results. Here, we propose a new direction by directly addressing the mechanisms underlying lack of responsiveness in PDOC, and using these to define our targets and the success of our intervention in the healthy brain first. We used fMRI to characterise the effects of tDCS on brain activity and dynamics during command following, a task typically used to clinically assess awareness. Anodal tDCS over M1 and cathodal tDCS over the cerebellum led to long-range changes in thalamo-cortical coupling associated with the ability to produce motor responses to command. This suggests that tDCS may allow PDOC patients to overcome the motor deficits at the root of their reduced responsiveness, improving their rehabilitation options and quality of life as a result.