Figure 4From: Real-time feature extraction of P300 component using adaptive nonlinear principal component analysis The pre-processed EEG signals that were band-passed. The EEG signals were pre-processed using a sixth-order BPF with cut-off frequencies of 1 Hz (i.e., to remove the trend from low frequency bands) and 12 Hz (i.e., to remove unimportant information from high frequency bands).Back to article page