The Self in Disorders of Consciousness

The clinical examination of residual (self-) consciousness in severely brain-damaged patients remains challenging. This is because patients in coma, vegetative/unresponsive wakefulness, and minimally conscious states are by definition unable to communicate their subjective experiences. As a result, (self-) consciousness in this clinical population needs to be inferred. To date, this is feasible by presenting patients with attention-grabbing stimuli, such as their own name and own face, while measuring their brain activation with assisting technologies. Event-related potentials and functional neuroimaging studies using such stimuli are used to decipher the cognitive hierarchy of self-processing. Most studies show that brain responses are differential between unconscious and minimally conscious patients and that an atypically high level of brain activity in response to self-referential stimuli can work as a marker of favorable clinical outcome. Brain function during resting state further sheds light on the subjective counterpart of “unconstrained” cognition and has paved the way towards single-patient differentiation. Taken together, the experimental exploration of the “self” in pathological unconsciousness surpasses the functional localization of self-related cognition and suggests a dynamic system-level approach to the phenomenological complexity of subjectivity.