The role of the primate prefrontal cortex (PFC) in conscious perception is debated. The global neuronal workspace theory of consciousness predicts that PFC neurons should contain a detailed code of the current conscious contents. Previous research showed that PFC is indeed activated in paradigms of conscious visual perception, including no-report paradigms where no voluntary behavioral report of the percept is given, thus avoiding a conflation of signals related to visual consciousness with signals related to the report. Still, it has been argued that prefrontal modulation could reflect post-perceptual processes that may be present even in the absence of report, such as thinking about the perceived stimulus, therefore reflecting a consequence rather than a direct correlate of conscious experience. Here, we investigate these issues by recording neuronal ensemble activity from the macaque ventrolateral PFC during briefly presented visual stimuli, either in isolated trials in which stimuli were clearly perceived or in sequences of rapid serial visual presentation (RSVP) in which perception and post-perceptual processing were challenged. We report that the identity of each stimulus could be decoded from PFC population activity even in the RSVP condition. The first visual signals could be detected at 60 ms after stimulus onset and information was maximal at 150 ms. However, in the RSVP condition, 200 ms after the onset of a stimulus, the decoding accuracy quickly dropped to chance level and the next stimulus started to be decodable. Interestingly, decoding in the ventrolateral PFC was stronger compared to posterior parietal cortex for both isolated and RSVP stimuli. These results indicate that neuronal populations in the macaque PFC reliably encode visual stimuli even under conditions that have been shown to challenge conscious perception and/or substantially reduce the probability of post-perceptual processing in humans. We discuss whether the observed activation reflects conscious access, phenomenal consciousness, or merely a preconscious bottom-up wave.

中文翻译：

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无需报告或感知后处理即可快速解码来自前额整体的视觉刺激

灵长类动物前额叶皮层 (PFC) 在有意识感知中的作用存在争议。意识的全局神经元工作空间理论预测 PFC 神经元应该包含当前意识内容的详细代码。先前的研究表明，PFC 确实在有意识的视觉感知范式中被激活，包括没有给出感知的自愿行为报告的无报告范式，从而避免将与视觉意识相关的信号与与报告相关的信号混为一谈。尽管如此，有人认为前额叶调制可以反映即使在没有报告的情况下也可能存在的感知后过程，例如考虑感知到的刺激，因此反映的是结果，而不是意识体验的直接关联。这里，我们通过在简短呈现的视觉刺激期间记录猕猴腹外侧 PFC 的神经元集合活动来研究这些问题，无论是在清晰感知刺激的孤立试验中，还是在感知和感知后处理被进行的快速串行视觉呈现 (RSVP) 序列中挑战。我们报告说，即使在 RSVP 条件下，每个刺激的身份也可以从 PFC 群体活动中解码。第一个视觉信号可以在刺激开始后 60 毫秒被检测到，并且在 150 毫秒时信息最大。然而，在 RSVP 条件下，刺激开始后 200 毫秒，解码精度迅速下降到机会水平，下一个刺激开始可解码。有趣的是，对于孤立刺激和 RSVP 刺激，与后顶叶皮层相比，腹外侧 PFC 的解码更强。这些结果表明，猕猴 PFC 中的神经元群体即使在已被证明挑战有意识感知和/或显着降低人类感知后处理概率的条件下，也能可靠地编码视觉刺激。我们讨论观察到的激活是否反映了有意识的访问、现象意识，或者仅仅是一种前意识的自下而上的波。