Right but basically wrong: comments on Canales et al. 'A critical assessment of the consciousness by synchrony hypothesis'.

The authors are right in holding the view that neural synchrony does not seem to provide a solution for the 'hard problem of consciousness' (Chalmers 1996). They are also right in that most of the evidence presented for the role of neural synchronization in perceptual binding is correlative and not causal. They are essentially wrong in all their remaining points. It is true that neural synchrony does not solve the hard problem, but then, nobody has proposed a solution for the hard problem. It is not even clear that such a problem exists or that a scientific solution can ever be given to the hard problem (Dennett 1991). Certainly it is premature to make a definitive statement on this subject at the present stage of research. By contrast, neural synchrony does seem to be at least part of the neural correlates of consciousness, which ask what are the minimal neural activities and structures that are necessary and sufficient for a conscious act to take place (Crick & Koch, 1990). In a recent paper we have been able to show that, long-range synchrony correlates with visual awareness but local synchrony does not (Melloni et al. 2007). This result, suggests that synchronic activity inside a restricted cortical area remains unconscious and that consciousness arises only when 'all the brain' is informed via long-range synchronic interactions. It can be hypothesized that this would be the basis for the unified character of experiential consciousness. The authors correctly point to the correlative nature of most of the evidence supporting a role of neural synchrony both in consciousness and in visual feature binding. To our knowledge there is a single experiment showing the causal involvement of neural synchrony in an odor discrimination task (Stopfer et al. 1997). However it must be stated that the same holds true for all electrophysiology in all the fields of neuroscience. From the studies of Hubel and Wiesel on, essentially all electrophysiology consists of manipulating the stimuli, recording the neural response and proposing mechanisms based on the correlations found. The only alternative theory for visual binding (the cardinal cell theory, Barlow 1972) is also mostly based on correlative evidence with the only exception of a few works conducted by Shadlen and collaborators (Huk & Shadlen 2005) An argument is made against synchrony as a mechanism for consciousness because of the participation of synchrony in non-conscious (anesthetized) animals and in brain areas …