Can self-relevant stimuli help assessing patients with disorders of consciousness?
Hearing one's own first name automatically elicits a robust electrophysiological response, even in conditions of reduced consciousness like sleep. In a search for objective clues to superior cognitive functions in comatose patients, we looked for an optimal auditory stimulation paradigm mobilizing a large population of neurons. Our hypothesis was that wider ERPs would be obtained in response to the subject's own name (SON) when a familiar person uttered it. In 15 healthy awake volunteers, we tested a passive oddball paradigm with three different novels presented with the same probability (P = 0.02): SON uttered by a familiar voice (FV) or by an unknown voice (NFV) and a non-vocal stimulus (NV) which preserved most of the physical characteristics of SON FV. ERP (32 electrodes) and scalp current density (SCD) maps were analyzed. SON appeared to generate more robust responses related to involuntary attention switching (MMN/N2b, novelty P3) than NV. When uttered by a familiar person, the SON elicited larger response amplitudes in the late phase of novelty P3 (after 300 ms). Most important differences were found in the late slow waves where two components could be temporally and spatially dissociated. A larger parietal component for FV than for NFV suggested deeper high-level processing, even if the subjects were not required to explicitly differentiate or recognize the voices. This passive protocol could therefore provide a valuable tool for clinicians to test residual superior cognitive functions in uncooperative patients.