Event-related potentials in disorders of consciousness

Abstract

Event-related potential (ERP) is a useful method for assessment of covert cognitive functions in patients with severe disorders of consciousness (DoC). Having a poorer spatial resolution than fMRI, ERP possesses a high level of functional specificity and an excellent temporal resolution. ERP can be combined with different kinds of passive (pure stimulation) and active (instruction) tasks, which allow the investigator to check different cognitive abilities of the patients. ERP is a cheap, mobile, well-tested method; all recordings can be carried out immediately at a patient’s bedside. A very broad number of cognitive processes can be tested; however, these processes are not necessarily related to consciousness. Although instruction tasks directly testing conscious awareness have also been used in combination with ERP, it remains unclear whether ERP has any advantages as compared to fMRI, the analysis of EEG oscillations, or even electromyography. Several middle-sized studies indicate that ERP can provide reliable predictors of the outcome of DoC; however, the results of these studies are inconsistent as concerns the exact role of ERP components as outcome predictors. This may be only addressed through large, multicenter longitudinal studies.