Cluster separation index suggests usefulness of non-motor EEG channels in detecting wrist movement direction intention

The aim of the study was to select the best electroencephalogram features and channel locations for detection of wrist movement intentions. The detected intentions can be used in brain-computer interfaces (BCIs) either for direct control of an artificial or virtual hand, or they can be used as an underlying binary code for execution of other tasks, 28 channel EEG was recorded while a subject performed wrist movements in four directions. Four basic feature types were extracted in the time and frequency domains for each channel following optimized filtering of the signals. The signals were split into planning and execution segments, respectively. Various delays and anticipation lengths were taken into account for each of the features, thus totaling 93 different features. The potential performance of each feature and channel for use in the classification of the EEG signals was analyzed by estimating the relative class overlap using the Davies-Bouldin index (DBI), a widely used measure for estimating cluster separation. The best feature/channel configurations contained both channels that were close and channels that were far from motor areas. A statistical test using the channel/feature configurations that yielded the lowest 5% DBI values for motor and for non-motor channels yielded no significant difference (alpha = 0.05) between these two channel populations. The scope and depth of the study was limited. Plus, important parts of the signal had to be discarded to rule out interference stemming from saccadic eye movement. However, our results do suggest more attention should be paid to non-motor areas in ear linked EEG data even when investigating movement related BCIs