Effects of overt and covert attention on the steady-state visual evoked potential
Effects of overt and covert attention on the steady-state visual evoked potential
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DOI：
10.1016/j.neulet.2012.05.011
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发表时间：
2012-06-21
影响因子：
2.5
通讯作者：
Mueller, Matthias M.
中科院分区：
文献类型：
--
作者：
Walter, Sabrina;Quigley, Cliodhna;Mueller, Matthias M.
闪烁的刺激会以与驾驶刺激相同的频率激发大脑的振荡反应，即所谓的稳态视觉诱发电位(SSVEP)。SSVEP是一种强健的大脑信号，其幅度随着注意力的增加而增强，因此在非侵入性脑机接口(BCI)的开发和使用中发挥着重要作用。我们比较了当受试者直接盯着闪烁的静态点阵列(显性注意)时SSVEP幅度的调制，与当他们偷偷地将注意力转移到保持眼睛处于中央注视的点上时的调制。在被观察的地点执行辨别任务，以确保受试者按照指示转移注意力。水平眼球运动(允许显性注意，但避免隐性注意)由水平眼电图仪监测。与显性注意相比，受试者在隐性注意下的行为表现显著降低。相应地，外显注意对SSVEP波幅的调节幅度大于内隐注意。外显注意也改变了SSVEP波幅在头皮上的地形图分布。当刺激被明显注意时，在中央枕叶电极上引起的幅度最大，而当被秘密注意时，刺激在对侧的顶枕部位引起最大的幅度。因此，来源分析显示，无论被关注的视觉半球如何，早期视觉区域在显性注意中都有明显的中心位置来源。综上所述，这些结果证实了外显注意和内隐注意对SSVEP反应和任务绩效有质和量上的不同影响。此外，我们的结果表明，在明显注意的情况下导航SSVEP-BCI更可靠，并突出了为失去眼睛移动能力的患者开发BCI所面临的一些挑战。(C)2012爱思唯尔爱尔兰有限公司。保留所有权利。
Flickering stimuli evoke an oscillatory brain response with the same frequency as the driving stimulus, the so-called steady-state visual evoked potential (SSVEP). SSVEPs are robust brain signals whose amplitudes are enhanced with attention and thus play a major role in the development and use of non-invasive Brain-Computer Interfaces (BCIs). We compared the modulation of SSVEP amplitudes when subjects directly gazed at a flickering array of static dots (overt attention) to when they covertly shifted attention to the dots keeping their eyes at central fixation. A discrimination task was performed at the attended location to ensure that subjects shifted attention as instructed. Horizontal eye movements (allowed in overt attention but to be avoided in covert attention) were monitored by the horizontal electrooculogram.Subjects' behavioural performance was significantly reduced in covert attention compared to overt attention. Correspondingly, attentional modulation of SSVEP amplitudes by overt attention was larger in magnitude than for covert attention. Overt attention also changed the topographical distribution of SSVEP amplitudes on the scalp. Stimuli elicited the largest amplitudes at central occipital electrodes when they were overtly attended and at contralateral parieto-occipital sites when they were covertly attended. Accordingly, source analysis revealed clear centrally located sources in early visual areas in overt attention, regardless of the attended visual hemifield. Taken together these results affirm that overt and covert attention have qualitatively and quantitatively different effects on SSVEP responses as well as on task performance. Moreover, our results suggest that navigating SSVEP-BCIs with overt attention is more reliable and highlight some of the challenges in developing BCIs for patients who have lost the ability to move their eyes. (C) 2012 Elsevier Ireland Ltd. All rights reserved.