Bernstein Focus: Neurotechnology, Berlin, Germany.
J Neural Eng. 2012 Aug;9(4):045006. doi: 10.1088/1741-2560/9/4/045006. Epub 2012 Jul 25.
Motion visually evoked potentials (mVEPs) have recently been explored as input features for brain-computer interfaces, in particular for the implementation of visual spellers. Due to low contrast and luminance requirements, motion-based intensification is less discomforting to the user than conventional approaches. So far, mVEP spellers were operated in the overt attention mode, wherein eye movements were allowed. However, the dependence on eye movements limits clinical applicability. Hence, the purpose of this study was to evaluate the suitability of mVEPs for gaze-independent communication. Sixteen healthy volunteers participated in an online study. We used a conventional speller layout wherein the possible selections are presented at different spatial locations both in the overt attention mode (fixation of the target) and the covert attention mode (central fixation). Additionally, we tested an alternative speller layout wherein all stimuli are sequentially presented at the same spatial location (foveal stimulation), i.e. eye movements are not required for selection. As can be expected, classification performance breaks down when switching from the overt to the covert operation. Despite reduced performance in the covert setting, conventional mVEP spellers are still potentially useful for users with severely impaired eye movements. In particular, they may offer advantages--such as less visual fatigue--over spellers using flashing stimuli. Importantly, the novel mVEP speller presented here recovers good performance in a gaze-independent setting by resorting to the foveal stimulation.
运动视觉诱发电位（mVEPs）最近已被探索作为脑机接口的输入特征，特别是用于实现视觉拼写器。由于对比度和亮度要求较低，基于运动的增强方式比传统方法对用户的不适感更小。到目前为止，mVEP 拼写器一直以显性注意模式运行，在此模式下允许眼球运动。然而，对眼球运动的依赖限制了其临床适用性。因此，本研究旨在评估 mVEPs 用于无需注视的通信的适用性。16 名健康志愿者参加了在线研究。我们使用了传统的拼写器布局，其中可能的选择以不同的空间位置呈现，分别在显性注意模式（目标注视）和隐性注意模式（中心注视）下。此外，我们还测试了一种替代的拼写器布局，其中所有刺激都在相同的空间位置顺序呈现（中央凹刺激），即选择不需要眼球运动。可以预期，当从显性操作切换到隐性操作时，分类性能会下降。尽管在隐性设置下性能降低，但传统的 mVEP 拼写器对于眼球运动严重受损的用户仍然具有潜在的用途。特别是，它们可能比使用闪烁刺激的拼写器具有更少视觉疲劳的优势。重要的是，这里提出的新型 mVEP 拼写器通过采用中央凹刺激在无需注视的设置中恢复了良好的性能。
