Kinsey K, Anderson S J, Hadjipapas A, Nevado A, Hillebrand A, Holliday I E
School of Life and Health Sciences, Aston University, The Wellcome Trust Laboratory for MEG Studies, Birmingham B4 7ET, UK.
Int J Psychophysiol. 2009 Sep;73(3):265-72. doi: 10.1016/j.ijpsycho.2009.04.004. Epub 2009 Apr 24.
We used magnetoencephalography (MEG) to examine the nature of oscillatory brain rhythms when passively viewing both illusory and real visual contours. Three stimuli were employed: a Kanizsa triangle; a Kanizsa triangle with a real triangular contour superimposed; and a control figure in which the corner elements used to form the Kanizsa triangle were rotated to negate the formation of illusory contours. The MEG data were analysed using synthetic aperture magnetometry (SAM) to enable the spatial localisation of task-related oscillatory power changes within specific frequency bands, and the time-course of activity within given locations-of-interest was determined by calculating time-frequency plots using a Morlet wavelet transform. In contrast to earlier studies, we did not find increases in gamma activity (>30 Hz) to illusory shapes, but instead a decrease in 10-30 Hz activity approximately 200 ms after stimulus presentation. The reduction in oscillatory activity was primarily evident within extrastriate areas, including the lateral occipital complex (LOC). Importantly, this same pattern of results was evident for each stimulus type. Our results further highlight the importance of the LOC and a network of posterior brain regions in processing visual contours, be they illusory or real in nature. The similarity of the results for both real and illusory contours, however, leads us to conclude that the broadband (<30 Hz) decrease in power we observed is more likely to reflect general changes in visual attention than neural computations specific to processing visual contours.
我们使用脑磁图(MEG)来研究在被动观察虚幻和真实视觉轮廓时振荡脑节律的性质。采用了三种刺激:一个卡尼萨三角;一个叠加了真实三角形轮廓的卡尼萨三角;以及一个控制图形,其中用于形成卡尼萨三角的角元素被旋转以消除虚幻轮廓的形成。使用合成孔径磁力测量法(SAM)分析MEG数据,以实现特定频段内与任务相关的振荡功率变化的空间定位,并通过使用莫雷小波变换计算时频图来确定给定感兴趣位置内的活动时间进程。与早期研究不同,我们没有发现对虚幻形状的伽马活动(>30Hz)增加,而是在刺激呈现后约200毫秒出现10 - 30Hz活动的减少。振荡活动的减少主要在纹外区域明显,包括枕外侧复合体(LOC)。重要的是,每种刺激类型都出现了相同的结果模式。我们的结果进一步强调了LOC和后脑区域网络在处理视觉轮廓方面的重要性,无论它们是虚幻的还是真实的。然而,真实和虚幻轮廓结果的相似性使我们得出结论,我们观察到的宽带(<30Hz)功率下降更可能反映视觉注意力的一般变化,而不是处理视觉轮廓特有的神经计算。