Department of Psychology and Center for Neural Science, New York University, New York, New York 10003, USA.
J Neurosci. 2013 Jun 5;33(23):9635-43. doi: 10.1523/JNEUROSCI.4612-12.2013.
A salient visual stimulus can be rendered invisible by presenting it to one eye while flashing a mask to the other eye. This procedure, called continuous flash suppression (CFS), has been proposed as an ideal way of studying awareness as it can make a stimulus imperceptible for extended periods of time. Previous studies have reported robust suppression of cortical activity in higher visual areas during CFS, but the role of primary visual cortex (V1) is still controversial. In this study, we resolve this controversy on the role of V1 in CFS and also begin characterizing the computational processes underlying CFS. Early visual cortical activity was measured with functional magnetic resonance imaging while human subjects viewed stimuli composed of target and mask, presented to the same or different eyes. Functional MRI responses in early visual cortex were smaller when target and mask were in different eyes compared with the same eye, not only for the lowest contrast target rendered invisible by CFS, but also for higher contrast targets, which were visible even when presented to the eye opposite the mask. We infer that CFS is based on modulating the gain of neural responses, akin to reducing target contrast.
将视觉刺激呈现给一只眼睛，同时向另一只眼睛闪烁掩蔽图形，这样一个显著的视觉刺激就可以变得不可见。这种方法被称为连续闪光抑制（CFS），它被提议作为一种研究意识的理想方法，因为它可以使刺激在很长一段时间内无法被察觉。先前的研究报告称，在 CFS 期间，高级视觉区域的皮质活动受到强烈抑制，但初级视觉皮层（V1）的作用仍存在争议。在这项研究中，我们解决了 V1 在 CFS 中的作用的争议，并开始描述 CFS 背后的计算过程。当人类受试者观看由目标和掩蔽图形组成的刺激时，我们使用功能磁共振成像测量了早期视觉皮层的活动，这些刺激被呈现给同一只或不同的眼睛。与目标和掩蔽图形呈现给同一只眼睛相比，当它们呈现给不同的眼睛时，早期视觉皮层的功能磁共振成像响应更小，这不仅适用于 CFS 使最低对比度的目标变得不可见的情况，也适用于即使呈现给与掩蔽图形相对的眼睛也能看见的更高对比度的目标。我们推断，CFS 是基于调节神经反应的增益，类似于降低目标对比度。
