Expanding the discussion: Revision of the fundamental assumptions framing the study of the neural correlates of consciousness

Decoding perceptual awareness across the brain with a no-report fMRI masking paradigm

Does perceptual awareness arise within the sensory regions of the brain or within higher-level regions (e.g., the frontal lobe)? To answer this question, researchers traditionally compare neural activity when observers report being aware versus being unaware of a stimulus. However, it is unclear whether the resulting activations are associated with the conscious perception of the stimulus or the post-perceptual processes associated with reporting that stimulus. To address this limitation, we used both report and no-report conditions in a visual masking paradigm while participants were scanned using functional MRI (fMRI). We found that the overall univariate response to visible stimuli in the frontal lobe was robust in the report condition but disappeared in the no-report condition. However, using multivariate patterns, we could still decode in both conditions whether a stimulus reached conscious awareness across the brain, including in the frontal lobe. These results help reconcile key discrepancies in the recent literature and provide a path forward for identifying the neural mechanisms associated with perceptual awareness.

Are we really unconscious in "unconscious" states? Common assumptions revisited

In the field of consciousness science, there is a tradition to categorize certain states such as slow-wave non-REM sleep and deep general anesthesia as "unconscious". While this categorization seems reasonable at first glance, careful investigations have revealed that it is not so simple. Given that (1) behavioral signs of (un-)consciousness can be unreliable, (2) subjective reports of (un-)consciousness can be unreliable, and, (3) states presumed to be unconscious are not always devoid of reported experience, there are reasons to reexamine our traditional assumptions about "states of unconsciousness". While these issues are not novel, and may be partly semantic, they have implications both for scientific progress and clinical practice. We suggest that focusing on approaches that provide a more pragmatic and nuanced characterization of different experimental conditions may promote clarity in the field going forward, and help us build stronger foundations for future studies.

The Idiosyncrasy Principle: A New Look at Qualia

In the study of consciousness, qualia, the individual subjective experience, is neglected. It remains impenetrable because the objective perspective used for scientific investigations misses its subjective nature. In 1974, Thomas Nagel suggested that studying qualia requires an “objective phenomenology method” whose goal would be to describe the subjective character of experiences in an independent manner. We introduce a corresponding theoretical and experimental framework based on the “idiosyncrasy principle.” Accordingly, subjectivity depends on the idiosyncratic composition of physical properties to qualia. This allows conceptualizing an idiosyncratic transfer function between the world and its representation. The main challenge in delineating such a transfer function is to come up with an objective measure for another person’s perspective. Numerosity, as opposed to other perceived contents of the physical world, allows reporting subjective experience in an objective manner. On the basis of this unique attribute of numerosity, we suggest a tentative neurocognitive research plan aimed at delineating such idiosyncratic transfer functions, permitting one person to adopt the perspective of another and linking qualia to its mechanism.

Consciousness as the Temporal Propagation of Information

Our ability to understand the mind and its relation to the body is highly dependent on the way we define consciousness and the lens through which we study it. We argue that looking at conscious experience from an information-theory perspective can help obtain a unified and parsimonious account of the mind. Today's dominant models consider consciousness to be a specialized function of the brain characterized by a discrete neural event. Against this background, we consider subjective experience through information theory, presenting consciousness as the propagation of information from the past to the future. We examine through this perspective major characteristics of consciousness. We demonstrate that without any additional assumptions, temporal continuity in perception can explain the emergence of volition, subjectivity, higher order thoughts, and body boundaries. Finally, we discuss the broader implications for the mind-body question and the appeal of embodied cognition.