The science of consciousness depends on experimental paradigms that compare conscious and unconscious processing. This review highlights a class of paradigms called "conscious interpretation," in which an object is consciously perceived as a set of features, but the interpretation of that set alternates in consciousness. The authors compare these paradigms with other types and review past and recent studies. They propose that for certain stimuli with a hierarchy of interpretations, conscious experience is drawn toward the higher-level interpretation and cannot revert to the lower level. The paper discusses how theories of consciousness might incorporate constraints arising from conscious interpretation.
A fundamental feature of consciousness is that its contents depend on its state. The authors propose that both state and contents depend on the activity of cortical layer 5 pyramidal (L5p) neurons. These neurons couple cortico-cortical and thalamo-cortical loops, forming a thalamo-cortical broadcasting system where L5p cells are central. This coupling corresponds to the coupling between state and contents of consciousness. The perspective predicts that cortical processing without L5p neurons will be unconscious, suggesting L5p neurons have a central role in the mechanisms underlying consciousness.