Guger Technologies OG, Graz, Austria. Department of Computational Perception, Johannes Kepler University, Linz, Austria.
J Neural Eng. 2018 Jun;15(3):036001. doi: 10.1088/1741-2552/aaa9f6. Epub 2018 Jan 23.
Several neuroimaging studies have demonstrated that the ventral temporal cortex contains specialized regions that process visual stimuli. This study investigated the spatial and temporal dynamics of electrocorticographic (ECoG) responses to different types and colors of visual stimulation that were presented to four human participants, and demonstrated a real-time decoder that detects and discriminates responses to untrained natural images.
ECoG signals from the participants were recorded while they were shown colored and greyscale versions of seven types of visual stimuli (images of faces, objects, bodies, line drawings, digits, and kanji and hiragana characters), resulting in 14 classes for discrimination (experiment I). Additionally, a real-time system asynchronously classified ECoG responses to faces, kanji and black screens presented via a monitor (experiment II), or to natural scenes (i.e. the face of an experimenter, natural images of faces and kanji, and a mirror) (experiment III). Outcome measures in all experiments included the discrimination performance across types based on broadband γ activity.
Experiment I demonstrated an offline classification accuracy of 72.9% when discriminating among the seven types (without color separation). Further discrimination of grey versus colored images reached an accuracy of 67.1%. Discriminating all colors and types (14 classes) yielded an accuracy of 52.1%. In experiment II and III, the real-time decoder correctly detected 73.7% responses to face, kanji and black computer stimuli and 74.8% responses to presented natural scenes.
Seven different types and their color information (either grey or color) could be detected and discriminated using broadband γ activity. Discrimination performance maximized for combined spatial-temporal information. The discrimination of stimulus color information provided the first ECoG-based evidence for color-related population-level cortical broadband γ responses in humans. Stimulus categories can be detected by their ECoG responses in real time within 500 ms with respect to stimulus onset.
几项神经影像学研究表明，腹侧颞叶皮层包含专门处理视觉刺激的区域。本研究调查了向四名人类参与者展示不同类型和颜色的视觉刺激时，脑电皮层电图（ECoG）反应的空间和时间动态，并展示了一个实时解码器，该解码器可以检测和区分对未经训练的自然图像的反应。
当参与者观看七种类型的彩色和灰度视觉刺激（人脸、物体、身体、线条图、数字以及汉字和平假名字符的图像）时，记录参与者的 ECoG 信号，从而产生 14 种用于区分的类别（实验 I）。此外，一个实时系统异步地对通过监视器呈现的人脸、汉字和黑屏（实验 II）或自然场景（即实验者的脸、汉字和自然图像以及镜子）的 ECoG 反应进行分类（实验 III）。所有实验的结果指标都包括基于宽带 γ 活动的跨类型区分性能。
在不进行颜色分离的情况下，实验 I 表明在七种类型之间进行区分的离线分类准确率为 72.9%。进一步区分灰度与彩色图像的准确率达到 67.1%。区分所有颜色和类型（14 类）的准确率为 52.1%。在实验 II 和 III 中，实时解码器正确检测到 73.7%的人脸、汉字和黑屏计算机刺激的反应和 74.8%呈现的自然场景的反应。
可以使用宽带 γ 活动检测和区分七种不同的类型及其颜色信息（灰度或颜色）。最大的分类性能是针对组合的时空信息。刺激颜色信息的区分提供了人类皮质宽带 γ 反应中与颜色相关的群体水平的第一个基于 ECoG 的证据。刺激类别可以实时检测到，其 ECoG 反应相对于刺激开始的时间延迟为 500 毫秒。
