Anterior cingulate activity and the self in disorders of consciousness

OBJECTIVES: The aim of this study was to investigate the relationship between medial cortical activation and the presence of self and consciousness in healthy subjects and patients with vegetative state and minimally conscious state using functional magnetic resonance imaging (fMRI). EXPERIMENT DESIGN: We first conducted two fMRI experiments in healthy subjects to identify brain regions specifically associated with self-perception through the use of different auditory stimuli that had different grades of self-relatedness. We then applied these regions as functional localizers to examine the relationship between neural activity changes during self-relatedness and consciousness level in the patients with disorders of consciousness (DOC). PRINCIPAL OBSERVATIONS: We demonstrated recruitment of various anterior medial cortical regions including the anterior cingulate cortex (ACC) in healthy subjects during auditory perception of self-related stimuli. We further showed that patients with DOC showed signal changes in the ACC during auditory perception of self-related stimuli. Finally, it was shown that these signal changes correlate with the level of consciousness in the patients with DOC. CONCLUSION: The degree of consciousness in patients with DOC was correlated with neural activity in the ACC induced by self-related stimuli. Our results not only shed light on the pathophysiology of DOC, but may also suggest a useful neural, and thus diagnostic, marker of the dysfunction of consciousness in vegetative patients.