Being conscious is a profound aspect of human existence, and understanding its function and its inception is considered one of the truly grand scientific challenges. However, the nature of consciousness remains enigmatic, to a large part because “being conscious” can refer to both the content (phenomenology) and the level (arousal) of consciousness, and how these different aspects are related remains unclear. To empirically assess the relation between level and content of consciousness, we manipulated these two aspects by presenting stimuli consciously or non-consciously and by using Propofol sedation, while brain activity was measured using fMRI. We observed that sedation affected both conscious and non-conscious processes but at different hierarchical levels; while conscious processing was altered in higher-order regions (the intraparietal sulcus) and spared sensory areas, the opposite effect was observed for non-conscious processing. The observation that Propofol affected non-conscious processing calls for a reconsideration of what kind of information one can gain on “consciousness” from recording neural responses to sedation without considering both (content) conscious and (content) non-conscious processing.

有意识是人类存在的一个深刻方面，理解它的功能和它的起源被认为是真正伟大的科学挑战之一。然而，意识的本质仍然是个谜，这在很大程度上是因为“有意识”既可以指意识的内容（现象学）也可以指意识的水平（唤醒），而这些不同方面如何相关仍不清楚。为了经验性地评估意识水平和内容之间的关系，我们通过有意识或无意识地呈现刺激以及使用异丙酚镇静剂来操纵这两个方面，而使用 fMRI 测量大脑活动。我们观察到镇静作用影响有意识和无意识的过程，但在不同的层次上；虽然意识处理在高阶区域（顶内沟）和感觉区域有所改变，但在无意识处理中观察到相反的效果。异丙酚影响无意识处理的观察要求重新考虑在不考虑（内容）有意识和（内容）无意识处理的情况下，通过记录对镇静剂的神经反应可以获得什么样的“意识”信息。