Department of Basic Psychology I, Complutense University of Madrid (UCM), 28223 Pozuelo de Alarcón, Madrid, Spain; Laboratory for Clinical Neuroscience, Centre for Biomedical Technology, Technical University of Madrid (UPM), Campus Montegancedo, 28223 Pozuelo de Alarcón, Madrid, Spain.
Laboratory for Clinical Neuroscience, Centre for Biomedical Technology, Technical University of Madrid (UPM), Campus Montegancedo, 28223 Pozuelo de Alarcón, Madrid, Spain; CEI Campus Moncloa, UCM-UPM, Avenida Complutense s/n, 28040 Madrid, Spain.
Neuroimage. 2014 Feb 1;86:470-9. doi: 10.1016/j.neuroimage.2013.10.037. Epub 2013 Nov 1.
To perceive a coherent environment, incomplete or overlapping visual forms must be integrated into meaningful coherent percepts, a process referred to as "Gestalt" formation or perceptual completion. Increasing evidence suggests that this process engages oscillatory neuronal activity in a distributed neuronal assembly. A separate line of evidence suggests that Gestalt formation requires top-down feedback from higher order brain regions to early visual cortex. Here we combine magnetoencephalography (MEG) and effective connectivity analysis in the frequency domain to specifically address the effective coupling between sources of oscillatory brain activity during Gestalt formation. We demonstrate that perceptual completion of two-tone "Mooney" faces induces increased gamma frequency band power (55-71Hz) in human early visual, fusiform and parietal cortices. Within this distributed neuronal assembly fusiform and parietal gamma oscillators are coupled by forward and backward connectivity during Mooney face perception, indicating reciprocal influences of gamma activity between these higher order visual brain regions. Critically, gamma band oscillations in early visual cortex are modulated by top-down feedback connectivity from both fusiform and parietal cortices. Thus, we provide a mechanistic account of Gestalt perception in which gamma oscillations in feature sensitive and spatial attention-relevant brain regions reciprocally drive one another and convey global stimulus aspects to local processing units at low levels of the sensory hierarchy by top-down feedback. Our data therefore support the notion of inverse hierarchical processing within the visual system underlying awareness of coherent percepts.
为了感知一个连贯的环境，不完整或重叠的视觉形式必须被整合为有意义的连贯感知，这个过程被称为“格式塔”形成或感知完成。越来越多的证据表明，这个过程涉及到分布式神经元集合中的振荡神经元活动。另一条独立的证据表明，格式塔形成需要来自大脑高级区域的自上而下的反馈到早期视觉皮层。在这里，我们结合脑磁图（MEG）和频域中的有效连接分析，专门研究格式塔形成过程中振荡脑活动源之间的有效耦合。我们证明，两色调“Mooney”面孔的感知完成会在人类早期视觉、梭状回和顶叶皮层中引起伽马频带功率（55-71Hz）的增加。在这个分布式神经元集合中，梭状回和顶叶的伽马振荡器在 Mooney 面孔感知过程中通过前向和后向连接耦合，表明这些高级视觉脑区之间的伽马活动相互影响。关键的是，早期视觉皮层中的伽马波段振荡被来自梭状回和顶叶的自上而下的反馈连接调制。因此，我们提供了一种格式塔感知的机制解释，其中特征敏感和空间注意相关脑区的伽马振荡相互驱动，并通过自上而下的反馈将全局刺激方面传达给低水平的感觉层次的局部处理单元。因此，我们的数据支持了在视觉系统中存在意识的连贯感知的逆层次处理的概念。
