Masking disrupts reentrant processing in human visual cortex
Masking disrupts reentrant processing in human visual cortex
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DOI：
10.1162/jocn.2007.19.9.1488
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发表时间：
2007-09-01
影响因子：
3.2
通讯作者：
Lamme, V. A. F.
中科院分区：
文献类型：
--
作者：
Fahrenfort, J. J.;Scholte, H. S.;Lamme, V. A. F.
在掩蔽中，通过在第一个刺激之后不久呈现第二个刺激，使刺激不可见。多年来，作者通常通过假设一些早期破坏过程来解释掩蔽。在这些前馈型的解释中，掩蔽以某种方式“赶上”目标刺激，通过横向或通道间抑制破坏其处理。然而，近年来的研究表明，视觉感知，尤其是视觉意识本身，可能强烈依赖于从高级视觉区域到低级视觉区域的皮质-皮质反馈连接。这使得一些研究人员提出，掩蔽的有效性来自选择性地中断这些重入过程。在这个实验中，我们使用脑电图测量来确定在非掩蔽（可见）和掩蔽（不可见）条件下检测纹理定义的正方形时，人类视觉皮层中发生了什么。在掩蔽条件下，通常与重入加工相关的脑电图衍生物是不存在的。此外，如头皮表面拉普拉斯电流源密度图所示，纹外视觉区仍然在早期被可见和不可见的刺激激活。这最终表明，前馈处理被保存，即使当主体性能是在由客观措施确定的机会。从这些结果中，我们得出结论，掩蔽来自其有效性，至少部分地，从中断重入处理，从而干扰图形-背景分割和视觉意识本身的神经机制。
In masking, a stimulus is rendered invisible through the presentation of a second stimulus shortly after the first. Over the years, authors have typically explained masking by postulating some early disruption process. In these feedforward-type explanations, the mask somehow "catches up" with the target stimulus, disrupting its processing either through lateral or interchannel inhibition. However, studies from recent years indicate that visual perception-and most notably visual awareness itself-may depend strongly on cortico-cortical feedback connections from higher to lower visual areas. This has led some researchers to propose that masking derives its effectiveness from selectively interrupting these reentrant processes. In this experiment, we used electroencephalogram measurements to determine what happens in the human visual cortex during detection of a texture-defined square under nonmasked (seen) and masked (unseen) conditions. Electroencephalogram derivatives that are typically associated with reentrant processing turn out to be absent in the masked condition. Moreover, extrastriate visual areas are still activated early on by both seen and unseen stimuli, as shown by scalp surface Laplacian current source-density maps. This conclusively shows that feedforward processing is preserved, even when subject performance is at chance as determined by objective measures. From these results, we conclude that masking derives its effectiveness, at least partly, from disrupting reentrant processing, thereby interfering with the neural mechanisms of figure-ground segmentation and visual awareness itself.