Event-related brain potential modulation in patients with severe brain damage

Objective: The limited evidence and inconsistency of purposeful behaviors in patients in a minimally conscious state (MCS) asks for objective electrophysiological marker of the level of consciousness. Here, a comparison between event-related potentials (ERPs) was investigated using different level of stimulus complexity. Methods: ERPs were recorded in seventeen patients, 6 of which in vegetative state (VS), 11 in MCS, and 10 controls. Three oddball paradigms with different level of complexity were applied: sine tones, the subject's own name versus sine tones and other first names. Latencies and amplitudes of N1 and P3 waves were compared. Results: Cortical responses were found in all MCS patients, and in 6 of 11 patients in VS. Healthy controls and MCS patients showed a progressive increase of P3 latency in relation to the level of stimulus complexity. No modulation of P3 latency was observed in the vegetative patients. Conclusions: These results suggest that the modulation of P3 latency related to stimulus complexity may represent an objective index of higher-order processing integration that predicts the recovery of consciousness from VS to MCS when clinical manifestations are inconsistent. Significance: Modulation of P3 latency related to stimulus complexity could provide valuable information about the cognitive capabilities of unresponsive patients. (C) 2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.