The potential for transcranial direct current stimulation to restore motor function in the vegetative state

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Recent improvements in the provision of intensive care have increased the chances of surviving the most severe brain injuries. Many of these patients progress to a state in which awareness and external responsiveness are either absent (i.e., the vegetative state) or greatly reduced (i.e., the minimally conscious state). It is now known that some of these patients retain a much higher level of awareness than could be expected by their clinical diagnoses, but they are simply unable to show it with their behaviours - trapped in their unresponsive bodies. Recently, my own research has provided an explanation for what happens in the brain to cause this unresponsive behaviour. Specifically, I identified a partial disruption in the flow of information between two brain regions that need to work together to allow for the voluntary control of movement, suggesting for the first time a potential target for interventions to restore motor control to those patients who, despite their diagnoses, retain a level of awareness. This project is aimed at assessing the potential for a non-invasive form of electrical brain stimulation, known as transcranial direct current stimulation (tDCS), to modulate the activity of the brain regions that control movement, and increase motor responsiveness as a result. In the proposed studies, healthy volunteers will receive tDCS, over different target regions and with different parameters (e.g., number of sessions, with / without an accompanying task, etc.), while their neural activity is recorded with functional magnetic resonance imaging (fMRI). By combining tDCS with fMRI, and using advanced analysis methods, I will be able to characterize the changes that occur in the relationships between the different regions in the motor network as a result of stimulation. This research has three primary objectives. First, I will map out the effects of tDCS over the brain motor network of interest. Second, I will explore potential enhancements in the effects of the stimulation with the use of multiple sessions and simultaneous stimulation and motor practice. Finally, I will investigate whether specific characteristics of the brain anatomy or function can predict the degree to which an individual will respond to the stimulation. The outcomes of this research will inform a longer-term research programme, with subsequent applications in groups of vegetative and minimally conscious patients themselves, with the final goal of developing effective and available interventions to treat these conditions. If successful, this programme will have a profound impact on the lives of the patients, and their families and care-givers, by providing the patients with a physical means of interacting with the world for the first time since their injuries.