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Neurosci."],"abstract":"<jats:p>Regaining communication abilities in patients who are unable to speak or move is one of the main goals in decoding brain waves for brain-computer interface (BCI) control. Many BCI approaches designed for communication rely on attention to visual stimuli, commonly applying an oddball paradigm, and require both eye movements and adequate visual acuity. These abilities may, however, be absent in patients who depend on BCI communication. We have therefore developed a response-based communication BCI, which is independent of gaze shifts but utilizes covert shifts of attention to the left or right visual field. We recorded the electroencephalogram (EEG) from 29 channels and coregistered the vertical and horizontal electrooculogram. Data-driven decoding of small attention-based differences between the hemispheres, also known as N2pc, was performed using 14 posterior channels, which are expected to reflect correlates of visual spatial attention. Eighteen healthy participants responded to 120 statements by covertly directing attention to one of two colored symbols (green and red crosses for \u201cyes\u201d and \u201cno,\u201d respectively), presented in the user\u2019s left and right visual field, respectively, while maintaining central gaze fixation. On average across participants, 88.5% (std: 7.8%) of responses were correctly decoded online. In order to investigate the potential influence of stimulus features on accuracy, we presented the symbols with different visual angles, by altering symbol size and eccentricity. The offline analysis revealed that stimulus features have a minimal impact on the controllability of the BCI. Hence, we show with our novel approach that spatial attention to a colored symbol is a robust method with which to control a BCI, which has the potential to support severely paralyzed people with impaired eye movements and low visual acuity in communicating with their environment.<\/jats:p>","DOI":"10.3389\/fnins.2020.591777","type":"journal-article","created":{"date-parts":[[2020,12,1]],"date-time":"2020-12-01T07:11:26Z","timestamp":1606806686000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":24,"title":["Impact of Stimulus Features on the Performance of a Gaze-Independent Brain-Computer Interface Based on Covert Spatial Attention Shifts"],"prefix":"10.3389","volume":"14","author":[{"given":"Christoph","family":"Reichert","sequence":"first","affiliation":[]},{"given":"Igor Fabian","family":"Tellez Ceja","sequence":"additional","affiliation":[]},{"given":"Catherine M.","family":"Sweeney-Reed","sequence":"additional","affiliation":[]},{"given":"Hans-Jochen","family":"Heinze","sequence":"additional","affiliation":[]},{"given":"Hermann","family":"Hinrichs","sequence":"additional","affiliation":[]},{"given":"Stefan","family":"D\u00fcrschmid","sequence":"additional","affiliation":[]}],"member":"1965","published-online":{"date-parts":[[2020,12,1]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"2686","DOI":"10.1109\/IEMBS.2010.5626548","article-title":"A novel brain-computer interface based on the rapid serial visual presentation paradigm","author":"Acqualagna","year":"2010","journal-title":"Proceedings of the 2010 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC\u201910"},{"key":"B2","doi-asserted-by":"publisher","first-page":"1021","DOI":"10.1109\/NER.2013.6696110","article-title":"Towards a brain computer interface based on the N2pc event-related potential","author":"Awni","year":"2013","journal-title":"Proceedings of the International IEEE\/EMBS Conference on Neural Engineering, NER"},{"key":"B3","doi-asserted-by":"publisher","DOI":"10.3389\/fnins.2010.00019","article-title":"A tactile P300 brain-computer interface.","volume":"4","author":"Brouwer","year":"2010","journal-title":"Front. 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