Severe brain injury is a leading cause of death and disability. Following severe brain injury diagnosis is difficult and errors frequently occur. Recent findings in clinical neuroscience may offer a solution. Neuroimaging has been used to detect preserved cognitive function and awareness in some patients clinically diagnosed as being in a vegetative state. Remarkably, neuroimaging has also been used to communicate with some vegetative patients through a series of yes/no questions. Some have speculated that, one day, this method may allow (...) severely brain-injured patients to make medical decisions. Yet, skepticism is rife, due in part to the inherent difficulty of assessing decision-making capacity through neuroimaging communication. In this thesis, I provide the first systematic analysis of this problem. I present and defend a strategy for assessing decision-making capacity in brain-injured patients who can only communicate through neuroimaging. (shrink)