Appelbaum L Gregory, Wade Alex R, Vildavski Vladimir Y, Pettet Mark W, Norcia Anthony M
The Smith-Kettlewell Eye Research Institute, San Francisco, California 94115, USA.
J Neurosci. 2006 Nov 8;26(45):11695-708. doi: 10.1523/JNEUROSCI.2741-06.2006.
Lateral occipital cortical areas are involved in the perception of objects, but it is not clear how these areas interact with first tier visual areas. Using synthetic images portraying a simple texture-defined figure and an electrophysiological paradigm that allows us to monitor cortical responses to figure and background regions separately, we found distinct neuronal networks responsible for the processing of each region. The figure region of our displays was tagged with one temporal frequency (3.0 Hz) and the background region with another (3.6 Hz). Spectral analysis was used to separate the responses to the two regions during their simultaneous presentation. Distributed source reconstructions were made by using the minimum norm method, and cortical current density was measured in a set of visual areas defined on retinotopic and functional criteria with the use of functional magnetic resonance imaging. The results of the main experiments, combined with a set of control experiments, indicate that the figure region, but not the background, was routed preferentially to lateral cortex. A separate network extending from first tier through more dorsal areas responded preferentially to the background region. The figure-related responses were mostly invariant with respect to the texture types used to define the figure, did not depend on its spatial location or size, and mostly were unaffected by attentional instructions. Because of the emergent nature of a segmented figure in our displays, feedback from higher cortical areas is a likely candidate for the selection mechanism by which the figure region is routed to lateral occipital cortex.
枕叶外侧皮质区域参与物体感知，但尚不清楚这些区域如何与初级视觉区域相互作用。使用描绘简单纹理定义图形的合成图像以及一种电生理范式，该范式使我们能够分别监测皮质对图形和背景区域的反应，我们发现了负责处理每个区域的不同神经元网络。我们显示器的图形区域用一种时间频率（3.0赫兹）标记，背景区域用另一种时间频率（3.6赫兹）标记。在同时呈现这两个区域时，使用频谱分析来分离对它们的反应。通过使用最小范数方法进行分布式源重建，并在一组根据视网膜拓扑和功能标准定义的视觉区域中，利用功能磁共振成像测量皮质电流密度。主要实验结果与一组对照实验相结合，表明图形区域而非背景区域优先被路由到外侧皮质。一个从初级区域延伸到更靠背部区域的独立网络优先对背景区域做出反应。与图形相关的反应对于用于定义图形的纹理类型大多是不变的，不依赖于其空间位置或大小，并且大多不受注意力指令的影响。由于我们显示器中分割图形的涌现性质，来自更高皮质区域的反馈很可能是图形区域被路由到枕叶外侧皮质的选择机制的候选因素。
