01900nas a2200169   4500008004100000022001400041245010800055210006900163260000800232300001400240490000800254520135900262100001801621700001701639700002601656856004801682       2017                        eng d  a1873-274700aEEG based zero-phase phase-locking value (PLV) and effects of spatial filtering during actual movement.0 aEEG based zerophase phaselocking value PLV and effects of spatia  cApr  a156–1640 v1303 aPhase-locking value (PLV) is a well-known feature in sensorimotor rhythm (SMR) based BCI. Zero-phase PLV has not been explored because it is generally regarded as the result of volume conduction. Because spatial filters are often used to enhance the amplitude (square root of band power (BP)) feature and attenuate volume conduction, they are frequently applied as pre-processing methods when computing PLV. However, the effects of spatial filtering on PLV are ambiguous. Therefore, this article aims to explore whether zero-phase PLV is meaningful and how this is influenced by spatial filtering. Based on archival EEG data of left and right hand movement tasks for 32 subjects, we compared BP and PLV feature using data with and without pre-processing by a large Laplacian. Results showed that using ear-referenced data, zero-phase PLV provided unique information independent of BP for task prediction which was not explained by volume conduction and was significantly decreased when a large Laplacian was applied. In other words, the large Laplacian eliminated the useful information in zero-phase PLV for task prediction suggesting that it contains effects of both amplitude and phase. Therefore, zero-phase PLV may have functional significance beyond volume conduction. The interpretation of spatial filtering may be complicated by effects of phase.1 aJian, Wenjuan1 aChen, Minyou1 aMcFarland, Dennis, J.  uhttp://www.ncbi.nlm.nih.gov/pubmed/2816119201805nas a2200145   4500008004100000022001400041245013800055210006900193260000800262520128000270100001801550700001701568700002601585856004801611       2017                        eng d  a1741-044400aUse of phase-locking value in sensorimotor rhythm-based brain-computer interface: zero-phase coupling and effects of spatial filters.0 aUse of phaselocking value in sensorimotor rhythmbased braincompu  cMar3 aPhase-locking value (PLV) is a potentially useful feature in sensorimotor rhythm-based brain-computer interface (BCI). However, volume conduction may cause spurious zero-phase coupling between two EEG signals and it is not clear whether PLV effects are independent of spectral amplitude. Volume conduction might be reduced by spatial filtering, but it is uncertain what impact this might have on PLV. Therefore, the goal of this study was to explore whether zero-phase PLV is meaningful and how it is affected by spatial filtering. Both amplitude and PLV feature were extracted in the frequency band of 10-15?Hz by classical methods using archival EEG data of 18 subjects trained on a two-target BCI task. The results show that with right ear-referenced data, there is meaningful long-range zero-phase synchronization likely involving the primary motor area and the supplementary motor area that cannot be explained by volume conduction. Another novel finding is that the large Laplacian spatial filter enhances the amplitude feature but eliminates most of the phase information seen in ear-referenced data. A bipolar channel using phase-coupled areas also includes both phase and amplitude information and has a significant practical advantage since fewer channels required.1 aJian, Wenjuan1 aChen, Minyou1 aMcFarland, Dennis, J.  uhttp://www.ncbi.nlm.nih.gov/pubmed/28343333