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/28161192