Some neurological patients with primary visual cortex (V1) lesions can guide their behavior based on stimuli presented to their blind visual field. One example of this phenomenon is the ability to discriminate colors in the absence of awareness. These so-called patients with blindsight must have a neural pathway that bypasses V1, explaining their ability to unconsciously process stimuli. The pathways that have been most often hypothesized to be the cause of blindsight connect lateral geniculate nucleus (LGN) or superior colliculus (SC) to extrastriate cortex, most likely V5, and parietal areas. To test if similar pathways function in neurologically healthy individuals or if unconscious processing depends on early visual cortex, we disturbed the visibility of a chromatic stimulus with metacontrast masking (Experiment 1) or neuronavigated transcranial magnetic stimulation (TMS) of early visual cortex, exact target being retinotopically mapped V1 (Experiment 2). We measured unconscious processing using the redundant target effect (RTE), which is the speeding up of reaction times in response to dual stimuli compared with one stimulus, when the task is to respond to any number of stimuli. An unconscious chromatic RTE was found when the visibility of the redundant chromatic stimulus was suppressed with a visual mask. When TMS was targeted to the correct retinotopic location of V1, and conscious perception of the redundant chromatic stimulus suppressed, the RTE was eliminated. Whether the elimination of unconscious RTE during TMS was exclusively due to disruption of V1 activity, or whether it was due to the possible interference with processing in V2 or even V3, is discussed. Based on our results and converging evidence from previous studies, we conclude that unconscious processing of chromatic information depends on the early visual cortex, in neurologically healthy participants.

中文翻译：

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早期视觉皮层的神经导航TMS消除了对色刺激的无意识处理。

一些具有原发性视觉皮层（V1）损伤的神经病患者可以根据对盲视场呈现的刺激来指导其行为。这种现象的一个例子是在没有意识的情况下辨别颜色的能力。这些所谓的盲人患者必须具有绕过V1的神经通路，这说明了他们无意识地处理刺激的能力。最常被认为是导致视力低下的途径将外侧膝状核（LGN）或上丘（SC）连接至外泌皮层，最有可能是V5和顶叶区域。为了测试类似的途径是否在神经系统健康的个体中起作用，或者无意识的加工是否取决于早期的视觉皮层，我们用元对比掩盖（实验1）或早期视觉皮层的神经导航经颅磁刺激（TMS）干扰了色刺激的可见性，确切的靶标是视网膜定位V1（实验2）。我们测量了使用冗余目标效应（RTE）的无意识过程，该效应是在任务要响应任意数量的刺激时，与一种刺激相比，对双重刺激的反应时间加快了。当用视觉掩模抑制了冗余色刺激的可见性时，发现了一个无意识的色RTE。当将TMS定位于V1的正确视网膜位置，并抑制了对多余色刺激的有意识感知时，RTE被消除了。讨论了在TMS期间消除无意识RTE是仅由于V1活动的中断，还是由于可能干扰了V2甚至V3中的处理而引起的。根据我们的结果和来自先前研究的越来越多的证据，我们得出结论，在神经系统健康的参与者中，对色度信息的无意识处理取决于早期的视觉皮层。