NEW APPLICATION OF THE Z-ESTIMATOR TO IDENTIFY THE COGNITIVE P300 IN NON-AVERAGED HUMAN BRAIN POTENTIALS

Electronic averaging is currently used for displaying event-related po tentials such as P300 from the electroencephalogram (EEG). However, th ere is a growing need for upgraded methods allowing cognitive componen ts to be identified in single trial brain responses. The Z estimation method has been adapted for the topographic testing of non-averaged sc alp recordings. Z values approximating +1 help validate a genuine P300 while failure to pass the Z test may suggest the spurious nature of a late positivity that mimicks a P300. Z testing can also identify inte rference from transient EEG alpha activity by showing alternations bet ween +1 and -1 values, as expected from an oscillating alpha generator In contrast with previous methods based on EEG recordings from a sing le scalp site, our topographic Z method takes into account 28 scalp si tes for single trials testing.