Kaiser Jochen, Bühler Mira, Lutzenberger Werner
MEG Center, Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Gartenstr. 29, 72076 Tübingen, Germany.
Neuroimage. 2004 Oct;23(2):551-60. doi: 10.1016/j.neuroimage.2004.06.033.
Electroencephalography studies have suggested that the perception of illusory figures is associated with increases in gamma-band activity putatively reflecting the formation of synchronously firing neuronal assemblies. Here we assessed magnetoencephalographic gamma-band activity, which has been shown to be topographically more focal than in electroencephalogram. In line with functional brain imaging findings, we hypothesized gamma-band activity over ventral visual stream areas. In addition, we expected that the analysis of oscillatory activity would provide information on the time courses and connectivity patterns of these activations. Following a paradigm previously assessed with electroencephalography, 16 adults were presented four types of stimuli at equal probabilities: illusory (Kanizsa) triangles, real triangles, no-triangle stimuli with rotated inducer disks, and curved illusory triangles serving as targets that subjects had to respond to. Induced oscillatory responses were compared between illusory triangles and no-triangle stimuli and between illusory and real triangles using a statistical probability mapping method. Illusory triangles were distinguished from no-triangles by increased activity at around 70 Hz over midline occipital cortex peaking at 240 ms after stimulus onset. This was followed by activations over bilateral lateral occipital areas at 430 ms. Illusory triangles differed from real triangles by increased spectral activity at 90 Hz over posterior parietal cortex between 100 and 450 ms after stimulus onset, suggesting an involvement of visual dorsal stream regions. Coherence analysis showed increased connectivity between posterior parietal and lateral occipital cortex. These findings suggest that illusory triangles are encoded in parallel by networks along the visual ventral and dorsal streams.
脑电图研究表明，对虚幻图形的感知与伽马波段活动的增加有关，这种活动据推测反映了同步放电的神经元组件的形成。在这里，我们评估了脑磁图伽马波段活动，已证明其在地形上比脑电图更具局灶性。与功能性脑成像结果一致，我们假设腹侧视觉流区域存在伽马波段活动。此外，我们预计对振荡活动的分析将提供有关这些激活的时间进程和连接模式的信息。按照先前用脑电图评估的范式，向16名成年人以相等概率呈现四种类型的刺激：虚幻（卡尼萨）三角形、真实三角形、带有旋转诱导盘的无三角形刺激以及作为目标的弯曲虚幻三角形，受试者必须对其做出反应。使用统计概率映射方法比较虚幻三角形与无三角形刺激之间以及虚幻与真实三角形之间的诱发振荡反应。虚幻三角形与无三角形的区别在于，刺激开始后240毫秒，中线枕叶皮质在70赫兹左右的活动增加并达到峰值。随后在430毫秒时双侧枕叶外侧区域被激活。虚幻三角形与真实三角形的不同之处在于，刺激开始后100至450毫秒，顶叶后皮质在90赫兹处的频谱活动增加，这表明视觉背侧流区域参与其中。相干分析显示顶叶后皮质与枕叶外侧皮质之间的连接性增加。这些发现表明，虚幻三角形由沿视觉腹侧和背侧流的网络并行编码。
