Leveraging multisensory neurons, circuits, brains, and bodies to study consciousness: from the outside-in and inside-out
The study of perceptual awareness is one of the ultimate frontiers in contemporary neuroscience. A host of neurobiological theories of consciousness exist, the vast majority of these originating from visual neurosciences and lying on a spectrum; from those posing the burden of explanation on the outside-in process of assembling sensory signals up the neuroaxis and ultimately leading to perception, to those arguing that perception is imposed from the inside-out onto the world given prior experience, bodily representations, and affordances. Interestingly, the majority of these theories speculate that information integration is central in engendering perception. In turn, here I attempted to re-align the study of perceptual awareness with our subjective experience of the world as inherently multisensory, and to leverage the process of multisensory integration – where integration is a de facto process – in the study of consciousness. Results suggest that insights derived from visual neuroscience may not be straightforwardly applied to the multisensory case, and instead suggest that contrarily to hypotheses from prominent theories of consciousness, perceptual awareness is graded and most faithfully tracked in the firing pattern of convergent rather than integrative neurons. On the other hand, findings do support the claim that peri-personal space is (at least partially) scaffolded on the process of multisensory integration, and that this space pre-reflectively encodes the location of the self as opposed to that of the body. Finally, results suggest that the mapping of peri-personal space may be utilized in diagnosing disorders of consciousness. Taken together, the present results suggest that the process of multisensory integration may inform already existent, and potentially give rise to new theories of perceptual awareness. Further, they highlight that perceptual awareness is a dynamic process – both within the brain being supported by reentrant circuit motif, and in the external milieu, with the world impacting neural processing and this latter one biasing environmental representations. Future work will aim to bridge the outside-in and inside-out approaches to consciousness, and may benefit from scrutinizing the interplay between perceptual awareness and active sensing, as well as between unisensory and multisensory likelihoods of perceptual metamers.