Distribution of channels selected for classification in various conditions over all subjects.
Scalp topographies indicate the prevalence of selection of different channels during the cross validation steps averaged over all subjects of a particular condition. Negative values indicate channels selected for negative ROC values, positive values indicate channels selected for positive ROC values. Values have been normalized to the maximum possible occurrences (nr subjects x nr of crossvalidation folds). The frontal cross indicates the Fz channel, the posterior cross indicates the Pz channel. Channels with negative ROC values are consistently selected from the frontal regions. For condition C1000, the channels with positive ROC values are concentrated over the parietal- and occipital areas, whereas for the faster conditions these are more diffuse.